Our Lady doesn't like to ride in the truck but there are times we insist. We put her favorite bed, disposable litter pan and small water bowl in the truck. She meows almost constantly and roams. Constantly petting her head, around her ears, is the only thing that calms her for a while. You think her voice would give out. Eventually (about 3 hrs later), she will attempt to lie down and nap but she fights it. Ever so often we hear a tiny little mew and we silently laugh. Tell her to be quiet and she meows back at us.
If the weather is not too cold or too hot, we do allow her to ride in the RV. She likes to lie on the carpet upstairs in the hall beside the bed. She gets to go to sleep (she is an all day sleeper and we think this is what makes her so cranky in the truck plus she doesn't like the truck sound) and seems not to be bothered at all. A couple of times we have found barf but that is usually when we have been traveling very rough roads. We stop about every hour for our own comfort and to check on her when she is in the RV. Most of the time, she meets us at the door with a very sleepy look on her face or she just stays lying in the floor where she sleeps. If we stop long enough, she goes to her food bowl or to the litter box or to get a drink.
I know riding in the RV is not the smoothest ride and sometimes not the safest if a door comes open or something decides to slide out of position. We have traveled with her for three years and now feel comfortable with whatever makes a better ride for her.
We do have a good size cage, which she hates, so rarely use it. In fact, it will be up for sale at the Goshen Rally - $40. It is large enough for two cats, a small litter pan, and small combo food/water dish. Great for keeping cats in when having RV work done inside. Lady loves service techs and enjoys their attention. So far we have had no problems with her getting out while RV is in for service. We just post a note on the door to remind techs she is inside.
Good luck with traveling with your fur kid!! It is an adventure