I am still confused by your question. Are there treking poles out there that are not adjustable in length? You definitely don't want those. Two piece vs. three piece, as long as they are also adjustable, doesn't matter that much and could be a personal preference, but:
1) you want strong poles. Many treking poles are designed to be light, which isn't really going to matter when snowshoeing. You don't really need poles on easy terrain; but if you are traversing something steep you don't want your pole accidently collapsing on you and sending you down into the snow bank.
2) you don't want shocks or anything that can freeze. The black diamond flicklocks can be adjusted wearing gloves. I am a bit skeptical about the twisty locks on lower sections of many poles both for freezing and collapsing, but lots of poles, including adjustable ski poles, come with those twisty mechanisms.
3) short is better than long, but almost any reasonable length can work and you can get used to it. This is not cross country skiing where you need properly sized poles to push, or downhill skiing where you need shorter poles for the descent. Even the flicklocks will move when I jam into them (more skiing then snowshoeing), and it is not unusual to notice at some point that I or someone I am with are using different length poles when snowshoeing. Often the snow on either side of the track is of dramatically different heights, or the snow is soft and so the poles are sinking, or the amount of snow on the sides or its firmness keeps changing as you go along, so pole length really comes out in the wash most of the time when snowshoeing.
4) if there really are "one piece" nonadjustable treking poles on the market, my guess is that those are a waste of money for snowshoeing, since you could get used beat up downhill ski poles for probably $5-10.