Had a bumper pull before I got the fifth wheel. I've had truck caps for at least the last 20 years before taking off the current one and getting the tonneau for the FW.
I liked and prefer the caps as I could carry the bikes and everything else imaginable inside while high and dry, as well as out of sight. Also could run the generator
inside the cap to keep the noise down. Could at the same time carry one or two of the canoes on the roof.
Cons to it were harder to access the stuff up front, can't carry stuff like loads of dirt without getting help to remove it. Blocks visibility somewhat, and it's one mor thing to wash and wax of you do sunch.
For caps... Had a Century long ago, good, cheap, lightweight aluminum that could be removed by one person. Had a Leer fiberglass job on my 06 GMC, kind of cheap paint
job, it had some rust, and the brake light
lens fogged. Got an ARE for the Ford I have now, better quality then either of the others I had, higher price too.
Have an Extang Trifecta tri-fold now, pretty cheap at under $400 for my 8' bed. Easy on and off so it can be removed for dirt and such. Simple to use, hides what's in the bed, no rails, snaps, or Velcro to mess with. It works fine but I do miss the cap.
If you want to be able to remove your cover I'd suggest either an aluminum cap or a tonneau cover. If you go with a cap, the more windows
the better, if you want to be able to put your bikes in, measure the bikes before you buy a cap. In my opinion a tonneau looks better.
The only thing that impacted towing in any way with either one was the visibility issue with a cap.