Sophie our older cats love to go rving. She wears a harness the entire time, is walked on a leash and has her own chair by the fire.
She likes to walk on the leash and it sure is a conversation starter to be walking a cat through a campground.
We have a class C and the litter box goes between the front seats when we stop. But as an indoor outdoor cat, she prefers to do her business outside, I have to be quick to scoop before she buries her poop.
We do not confine her while underway, but we do travel with a crate which we use when setting up or loading up to make sure she does not get out.
Charlie our other cat has not yet been camping. I do not think he will take to it was well as Sophie. He is much more skittish, does not like new people etc.
We also travel with one or two dogs, ours and my mum's.