There is no good putter fitting "system" out there at present because technology is not knowledge, it is a mechanism that someone designed to measure what happens when YOU make a stroke. Suppose you make a bad stroke? Will the technology tell you: "Hey, that stroke sucked." Will the technology take the stroke "data" measurements of a suboptimal stroke and then offer this advice: "In order to make a better stroke or even your best stroke, you need to do this (...) differently with your body and this is how you get that done (...)." Uh, obviously not. The PERSON standing there charging you money to use the technology's measurements will make that evaluation -- this person will either know what the measurements MEAN in terms of body action and changes or they won't. Based on what? Either this person will have study and experience and REAL KNOW-HOW in their mind to use in interpreting the measurement and so that they can communicate what to change and how or they won't.
IF the person interpreting the technology measurements KNOWS WHAT BODY ACTION RESULTS IN GOOD STROKES, then it is NOT the "system" that is helping, but the "coach." The odds that a person selling you putter fitting services with technology being a knowledgeable coach about HOW THE BODY OUGHT TO MOVE IN MAKING A GOOD STROKE are, shall we say, not great.
It is true that no putter fitting should go forward without first FIXING a flawed stroke movement. Can a technology "system" fix your stroke? No, it can only measure what happens when you make whatever stroke you make. A COACH has to interpret these measurements and then sort good from bad and then advise you WHAT TO CHANGE IN YOUR BODY ACTION THAT WILL IMPROVE THE STROKE (that will thereby generate better measurements). The technology in itself does not know good from bad data.
If the person standing beside the technology claims that the technology has a "model" of pro data that shows the difference between good and bad, they are making a false claim.
First, a "model" is an average, and average PGA pro strokes frankly aren't great at all. You might accept that the "model" pattern of movement COULD produce better strokes and better results than you currently know how to make, and if that is all you want, then by all means PAY FOR THE SYSTEM TO SHOW YOU THE MODEL AND HOW FAR OFF YOU PERSONALLY ARE, but you won't be paying for the system to "show you how to do it better." The system will just stand there and wait until some changes you make in a trial and error approach yield data measurements that look closer to the model data. Who helps you decide what changes are helpful? Now, you're out of the "system" and depending upon a person. That person better be a good knowledgeable coach who knows good from bad body action and how to teach you about doing it.
Second, whether the stroke measured by the technology is good or bad cannot be decided apart from the result of what happens in a putt -- does the putt go where the putter aimed, and does it roll nicely and arrive with the correct pace so that it follows the break (and does not blow thru the break or fall short of the break) and does the ball arrive at the cup and go down inside with nice terminal speed? This is basic "raw knowledge of results" (KR) feedback that today's technologies / systems don't even measure AT ALL. The measurements of what the putterhead was doing thru the impact zone is definitely NOT a measurement of KR. This means that today's technologies are not actually ABLE to let even a knowledgeable coach sort good from bad measurements. The coach can ONLY use the technologies helpfully by ADDING some capacity to monitor or measure what results. And of course the technologies aren't measuring thew body action either, except by interpretive inferences from whatever the putterhead does that gets measured. Without the knowledge of what resulted with the putt from the body action that moved putterhead in the measured pattern, the coach is helpless about this interpreting and sorting of the technology measurements.
This means the technology has to take into account the relationship between reading, aiming, stroke and pace control ("touch") -- but NO available technology / system does this today. These factors influence one another, and you cannot help a golfer by changing only the stroke apart from these other issues. For example, one prominent / expensive technology uses "model" data to change amateur strokes by making them fit the timing pattern of pro strokes, but does this without even measuring whether the different timing pattern affects touch in a good or bad way, or affects reading and aiming as well. YOU CANNOT AVOID ALTERING TOUCH WHEN YOU CHANGE TIMING PATTERNS IN THE STROKE, so doing this shifts a golfer out of the way he was getting touch with his old timing to a new timing without the KNOW-HOW for getting good touch with the new timing. Bad plan, folks.
So, it is POSSIBLE that the person offering putter fitting services is also a knowledgeable putting COACH, but that is pretty doubtful.
There are only two ways to gain KNOW-HOW: dig it out of the earth yourself with years of practice and exploration and paying attention to the differences between good and bad so that at the end of this laborious process you KNOW HOW TO MOVE and KNOW WHY to do it a certain way, or take a lesson from a good and knowledgeable COACH who can communicate the KNOW-HOW effectively to you so you get the KNOW-HOW from the communication process plus your exploration and knolwedgeable practice thereafter to "make it your own". Just getting the movement to generate good measurements is NOT, I repeat NOT, learning. Learning is gaining the conscious KNOW-HOW that accompanies and underlies a sound and competent movement, not just an expression of talent or temporary repetition. Without this KNOW-HOW there is never any future feedback that sorts good from bad, so there is never any steady improvement, no consistent repetition, and no self-coaching and self-correction in case the golfer gets off track mid-round.
So, yes, you need to FIX your movement before getting FIT to a putter, since the fitting process will cement WHATEVER STROKE YOU GET FIT TO. The trouble with a "system" (technology) is the false promise that it FIXES your stroke for the future in a sound way. That's TWO giant assumptions that are seldom, seldom true: 1) that the system or even the person operating the system can help you change your body action from bad to better or good or best (not unless the person is also a good putting coach), and 2) that the changes that show up during the putter fitting session are going to be permanent and will be the SAME movement that you make in the following months and years when using the putter that gets fit to you that day (not unless you extract or take away from the session real KNOW-HOW about the new movement pattern in terms of HOW TO DO IT and WHY). Good luck with that without checking out the PERSON -- is he a good putting coach or not?
Even IF the system / technology measurements PLUS the operator can change your body action in a sound way, there is still the main issue of WHAT DOES THIS MEAN FOR THE PUTTER DESIGN THAT BEST PROMOTES THE NEW MOTION? That also depends exclusively upon whether the operator is a good, knowledgeable putting coach who not only knows sound body action (setup postures and movement patterns and strategies), but also knows the cause-and-effect properties of putter design features and can use good judgment to know what matters and to what extent a feature matters when engaging in design feature trade-offs in the fitting process personalized to you. These sorts of judgments begin and end with the individual golfer's body, posture, and movement patterns -- I've never seen a technology or putter fitting system that even pays any attention to these issues, and certainly none that actually measures these aspects and then sorts good from bad and makes good judgments in the trade-offs.
Bottom line: there is no such thing as a effective putting coach "system" (technology) and you must depend entirely upon whether the PERSON using the technology knows what makes a good stroke in terms of body action, knows how to interpret the measurements of the technology for what they indicate about your movement, knows the cause-and-effect properties of putter design features, and knows the characteristics of the your individual body, posture, and movement patterns, AND knows how to communicate to you how to change your stroke to better so you gain real KNOW-HOW that carries forward on a permanent basis.
Does a good coach need ANY technology for fitting a golfer with a good putter? Not in the usual sense of "electronic" or "computer" technology. This sort of technology MAY be useful in the hands of a good coach, but the good coach doesn't really NEED this sort of technology to do a superior job of putter fitting. The coach needs to know what happens to the roll of the ball whether the stroke came from a good setup and movement and sent the ball squarely and solidly where the putter face aimed at address. (If the ball rolls where the face was aiming, and the pyutter face impacts the ball on the sweetspot of the putter face, ergo the impact was square thru the impact zone regardless of path. At the same time, concomitantly, if the balls rolls where the face was aimed and the putter face appeared to transit the impact zone squarely, ergo the stroke path was good even IF the impact on the ball was off to the side of the sweetspot a little, although perfectly solid impact would be better.) Then, the coach needs to know what to suggest for putter length, loft, lie, weighting, visual appearance, grip, etc., to promote good strokes from sound setups and motions.
The technologies out there today don't get this done -- they simply MEASURE and report the stroke you make then and there however you get it made. And the precision with which the technology measures this is grossly over-precise. This results in golfers "working at the gimmick of the technology during practice to make the numbers come out the same" while ignoring the KNOW-HOW of the movement -- working the puzzle posed by the device is NOT learning how to make a sound stroke. You get "perfect in practice" but in play the stroke you make is a different story.