Personally, I have an oversized duffelbag that will hold my pack, fully loaded, plus some other stuff. I definitely do not like putting a pack through airline handling with the straps exposed. That's just asking for buckles to get broken, straps torn or frames damaged.
If you put your hiking poles or other long skinny things in the same duffel, probably a good idea to have some extra-long straps and lash them to the pack so they don't shift around and get bent/broken. My hiking pole (I only use one) will fit diagonally in my large suitcase so if I am packing both the suitcase and duffel, I'll put the hiking pole in the hard-sided suitcase.
Pointy things like ice axes, crampons, etc., need appropriate caps or rubber bumpers on all the sharp bits so they don't poke your gear or someone else's. Ditto for the hiking poles...I leave the rubber tip on mine while it's packed and take it off for the trail. I have a set of the rubber gizmos for my crampons, as well. 12 rubber caps with a rubber pattern between them so they slip on the crampons but don't get lost individually. Plus, a rubber protector for the adze and pick on the ice axe and my own Delrin cap for the spike end. (I have access to a machine shop so I got fancy...you could cut one out of a couple of pieces of wood and a scrap of Masonite that would work just fine, too.)
You have to be sure that your pack, inside the duffel, is still within the luggage size allowance and do not overpack it. 20 kg or 44 pounds is a good limit. Much over that and you'll get zapped with an "oversize/weight" luggage charge. Of course, more and more airlines are charging for the second bag no matter what, so you might want to check with your airline whether one overweight bag is cheaper than two "normal" ones.