If I were full timing I would have fifth wheel, hands down. You see more fifths than anything at the many snowbird parks around here, but there are Cs and even truck campers, so anything is workable. I traded my fifth for my C because we drive more than we stop and the C works best for that. I don't recall the fifth having much more, if any, CCC than the C though. Who worries about such things!
I've met people who full time in smaller C's than that. Some pull trailers, or a loaded pickup, for their "stuff" but others have a lifestyle that fits what a small C can carry.
I've met a few singles full-timing in B's, and two different guys full-timing in Pop-up trailers.
It works the same for houses. Some people can't live in anything smaller than 4000 sq ft, others, particularly in cities in Europe and Asia, make do with 200 sq ft, which is like a 25 foot C.