The 2 posts above are pretty accurate but I want to expand on what they wrote. When we decided to get an RV more than 10 years ago I researched small Class C's, pickup campers, and Class B's.
Pickup campers range from lightweight popups with minimal facilities to large models that approach the liveability of a B. A 1/2 ton PU can easily carry the popups and is your best bet for off-roading. The larger, more comfortable campers require at least a 1 ton truck and most require dual rear wheels. They are not so great for off-roading because of their height, width, and high center of gravity. Overall, truck campers are great for people who already have a pickup truck or need one for other purposes. I decided against a pickup camper because I didn't need a pickup and because I didn't like the cabover sleeping arrangement.
I didn't see any small Class C's that had a floor plan that I liked. That, plus the generally poor construction quality of C's, nixed them for us.
That led us to a class B.