There is little if any comparison between a tow behind popup camper and a popup truck camper. We have had both. I think LynnandCarol is talking about a tow behind popup camper, they are much different from the TC popups.
Some of the popup truck campers do have canvas sides, I cannot speak to them. Our sides are a vinyl mesh product that is insulated and quite stiff. Most vinyl/canvas sections are only 18" to 24". They are held in suspension by either a gear drive or in some cases a spring setup. I cannot speak about the spring systems.
Our popup TC is an Outfitter it now has an electric screw gear drive holding the top up. From the factory it was a manual tooth gear drive, but we had it switched out at the factory. Both gear drive systems hold the fabric pretty taunt.
We have been in 50 mph to 60 mph per hour gusting mountain winds with our Outfitter and the sides are rock steady, no flapping or shaking. The heavy vinyl material does absorb the sound as well. With the jacks down we are pretty steady no different than a hard side model.
We had a Lance camper and there is little difference in comfort between the two styles, if any when setup. On the highway side winds affect the Outfitter much less than the Lance. The Lance was on an 8 foot box crew cab dually, it was bigger camper.
We have been in driving rain and snow again no flapping or loud noise like a tow behind popup camper. Yes, thunder can get loud, but no different than a hard side camper.
Good luck.