The point is, while population is power, concentrated population seems to be the way to go in Galciv.
Not in my estimation.

Maybe for certain unusual terrain situations, certain bonus picks, or other niche situations, skipping the borderline habitables would be a good idea. For most situations, it's not.
I know there are a couple of schools of thought about how to succeed on Maso. If we take the exploit-minded ones off the table, there are still some different ways to go. Skipping the poor worlds lets you move more quickly onto offense. Settling them gives you more potential long term. They do require an initial investment to weather the stage of bringing them up to PQ14. Below 14, they are LOSING money. They cost money. A PQ14 costs nothing. It doesn't bring you any income, but it doesn't cost you anything either. A PQ15 starts to bring in the income.
If you build the Terraformer, late game, then that combined with soil, habitat, and terraforming adds a whopping FIFTY PERCENT to PQ. If Earth starts as a 20, it will get to 30. 16's become 24's. 15's become 22's. Even a 12 becomes an 18. Terraforming costs an investment of 1000 bc in social spending per planet, of course, but you do all your planets at one time. Any planet not ready to go when the time comes will be left behind for all time.
Thus, if you are ever going to settle those borderline worlds, the time to do it is early, so they fulfill more of their potential later. Even a PQ12 that you settle late, though, will get to PQ15 without the pricey terraforming: +1 from soil, +1 from habitat, and +1 from the terraformer. That puts it at PQ15, and if you have managed to secure economic-boosting wonders, or you have eco bonus picks, or you mine one or more economic resources, or your survey ships finds a dozen or more +1% economic anomalies -- or any combination of the above -- you will probably get to where you have more economic boost than you can shake a stick at, and more than any of your large planets can make use of. The extra can help nudge those sad little border worlds into profitability, though.
A planet will easily bring in up to 4x its PQ in BC per turn. Past that, any extra gets nerfed HARD, but may still trickle in a few more pennies. Yet even unimproved, a PQ12 could bring in 50gpt. A PQ12 with soil/habitat/terraformer (PQ15 net) can bring in 65gpt. A PQ12 with soil/hab/terraforming/terraformer (PQ18 net) can bring in almost 80gpt. That picture looks better for natural PQ13 and 14.
Population IS power. And to get population onto those borderline habitables, you need morale. You need morale wonders, trade goods, starbase mines, bonus picks, and improvements. If you settle border worlds early, they will follow along slightly behind your other worlds. If you settle them late, you've got to run a different governor order that prioritizes morale improvements: soil, hab, entertainment, stadium, teleporters, stock market, in that order. You may have to cash rush some, but a natural PQ13 with soil, hab, The Terreformer effect, entertainment and stadium can grow to 10billion in pop, if you have secured morale boosting items (say, 250% morale boost or more). Morale boosters don't work on their own, though. They work to multiply the beneficial effects of your morale buildings. Thus, you've got to buy the entertainment and stadium, if you are settling after your main planets are done with all social spending. That's an investment, but once the planet grows its own population, you'll actually make it all back.
Having more planets doesn't make your population grow faster
Yes it does. The growth rate is capped per planet, thus adding more total planets raises your civ-wide growth curve ceiling.
I also avoid pq 15 planets unless there are many in one sector. My worst pq planet will build enough colony ships to park near any such planets in case I might be forced to colonize some pq 15 depending on who show up there first. If a minor civ or a weak major send a colony ship that way, I will gladly let them have the money pit.
EEP!
Ph34r the cultural power of a Maso AI holding two or more fully mined influence resources. PH34R them if they also have Galactic Monument, Hyper Distribution, and other influence wonders/goods.
I won't let a major settle anything within two sectors of my worlds if I can help it. I won't settle within two sectors of them if I can help it. Anything directly adjacent to a sector where they have a planet is at severe risk, unless you have loyalty and influence boosts of your own. I usually don't, yet I can still manage. Worst case, you've got to pour resources down the drain of building defensive cultural starbases in your own sectors just to fight off the neighbors. God help you if the same AI has four or more influence resources and some influence wonders.
I used to marvel at watching certain AI's be able to "move in" to someone else's terrain and start flipping their planets. Then I made the connection. Let there be no doubt, the most important two types of resources are influence and military, in that order. The more you own, the more the benefits stack up behind you. Morale and research are less urgent, because the first one is worth a lot but more may not be, while economics has a hard cap and rarely is more than one useful at all, other than for denial purposes.
Since you can never tell in advance who will end up controlling which resources, caution is the watchword for me. I only start getting cocky about culture if my diplomatic situation is secure and I have gained control of influence resources and wonders. I even know when I can be the rampaging menace who plops down 10 million colonists on a PQ13 in somebody else's sector and flips their worlds with tens of billions. Been there and done that! Fairly rare to be sitting that pretty, though.
I can see skipping the 13's and 14's. There's at least an argument to be made there, although I always grab them myself. But 15's? You gotta be kidding me.
By the by, I have played Kylearan's map. I'm in the process of assembling my report. And yes, I grabbed all five borderline habitables in his starting cluster. I'm just trying to figure out how to edit my player name and serial number INTO the save file so I can submit it to the Metaverse.
Until your best planets show signs of overcrowding, I don't think it is worth it to send your population away on some half decent planet where they will be LESS productive.
On this, we agree. That is NOT what you do. You send 20 or 30 million to PQ13's, 40 to 50 mil to 14's. And of course, you can mix and match those a bit. I've had to settle with a 100mil ship intended for greener pastures onto a 14. That's doable. Not so good if you have to land a ship with 200+ mil on a borderline, though.
Peeling 20 or 30 million off a planet hardly dents it. The borderlines don't need much population at first anyway. Heck, even ZERO would be doable. (Ever gotten the UP event that gives you a free planet with zero starting pop?)
What you do NOT do is launch your colony ships with the default "half" setting. NOT EVER. Don't do that. Don't send your population anywhere. Ever. Send out a few colonists. 100mil to 200mil in search of "anything yellow". More than 300 million ONLY if you already know of a PQ20+ your scouts have found. Send out small batches of 40 to 50mil to grab the 14's, or else that's all you CAN send out from secondary worlds that start building colony ships for you on the bigger maps.
I wish there was a button to toggle that would let me select colonists "10mil at a time" instead of 1mil. The most tedious aspect of GalCiv is like Diablo 1 purifying spring: sitting there clicking and clicking and clicking to fill 30 mil, 40 mil, 50 mil onto a colony ship, 1mil at a time. That is only necessary later in the game, when even the minimum amount the slider will let you send is WAY too much, but I do sometimes have to do some of that to correct a minimum 60mil off of earth down to the 40 I want to send to a PQ14, etc.
I admit it, sometimes I get lazy and send only 20 mil when the best result would be to send 40. I get tired of clicking.

SHOULD BE a way to send groups of 10mil at a time, so that 40 would be four clicks instead of forty clicks. Oh well.
For goodness sake, though, NEVER ship your population offworld. Choose a number of colonists appropriate to the destination, or to what you hope and expect to find out in the fog. I figured this out in my first game, but it bears pointing out to anybody who may be overlooking it. Never autolaunch colony ships, and try to match how many colonists you send with how many would be best useful at wherever you are sending them.
PQ13's and 14's if properly managed can be good assets. Ideally, you want to have all your planets settled by the time you are done researching a few techs. Usually takes about nine turns to research Communication, Translator, Diplomacy, Trade, Medical and Basic Environment. That's one turn apiece for the small fry, two for the bigger techs. If your economy is strong enough (depends on terrain, and how far your colony ships have to travel, on average) you may research all six techs in six turns. Worst case, it could take longer. And of course, sometimes some colony ships will lag behind, or if you are scouting WITH the colony ships, you may even have some left over (built too many) that you will waste one way or the other (letting the people rot in space, for a long long time on the hope of finding them a distant home later, or else merging the ship to an existing colony and wasting the ship).
If you go all colony ships until you believe you have built all you need or all you can reasonably grab, then you go all tech to get the early techs you need, while the straggler colony ships are en route, then you go all social... most if not all your planets will be founded when you start to spend on social, and they will all "grow up together". This may be the key to having the PQ13 and PQ14 worlds pay off. If you neglect them and "fill them in later", they will be forever behind the other planets, and thus never catch all the way up, because you will simply STOP spending on social when there is nothing useful left to build on your core crop of planets. If your borderlines "grow up" with the core planets, you can build "optional stuff" like Economic Exchange, Advanced Quality Control, Star System Defense and Galactic Research Center on your best worlds, while the slower ones are finishing their essentials like stock market.
The problem with being a builder in GalCiv is the inability to manage one planet at a time. You simply cannot designate extra social spending on some planets. Nor can you turn off social spending. If a planet is "done" and has nothing left you want to build, any social spending there is simply burned off to no useful end. Wasted. If that's happening at a lot of worlds, you are in a bad situation. Thus the worst thing you can do is to have most of your planets sitting around doing nothing while you build a wonder at your best producer. Wonders are best done in batches, spread out over your highest PQ worlds, which gives the lower PQ's "catch up time" on the basics. This, too, may be key to nurturing borderline worlds: a successful "whole civ" management of your economy, correctly identifying when to build wonders and which planets to use for the building.
No doubt that the governor is your friend. The ability to set the build order, to change it so easily, to adapt it, and even to have more than one queue going (though I usually stick with one) frees the player from untold tedium compared to other 4X games.
PQ 24 planets and up can have lots of people before overcrowding kicks in.
Overcrowding never kicks in. Your planets will not grow themselves below 50 morale. Therefore, if a planet gets crowded, it just stops growing in population. Morale below 50 comes from messing with your tax settings too often, sending WAY too many colonists on the colony ship, taking over a planet the AI has mismanaged, destroying improvements with WMD during invasion, or having an enemy paying to sabotage your morale. It does not happen from natural growth.
If a planet gets to 50 morale, so what? No biggie. You don't up-end your whole civ for that. In some cases, you can buy a morale improvement. Usually, I do nothing at all about it. Nothing extra that is. I do prioritize morale buildings. Only if my entire civ has low morale is there a problem, and it usually means I don't have enough morale improvement techs. Time to prioritize Interstellar Capitalism, Extravaganza or Teleportation, or perhaps to go after morale resources, trade goods, or techs like Viral Elimination.
I WANT my morale to start dropping. It means my pop growth has caught up with my infrastructure. What happens when you build Aphrodisiac? Your morale "goes down faster". Or in other words, your population grows faster and hits the current morale ceiling sooner. That's GOOD. Low morale is not always a bad sign. Sometimes it means you've plateaued.
Anyway, I settle the borderline habitables because I, at least, consider them to be assets. I can understand how different gameplay priorities and strategies would consider them as liabilities. A lot also depends on your trade situation, terrain, map parameters, and bonus picks.
- Sirian