As far as I know you can drive any RV with your current license. I drive my 40 foot Prevost with air brakes and tandem rear axles all over the place without trouble, at the posted car speed limit as well! It is governed to 75 mph so speeding is not much of an option on the interstate. I have talked with a few police about it and I am quite legal even when I have the trailer on the back. It's not nearly as bad to drive as it would seem.
Fuel milege is terrible, 4-6 mpg in the gasser if you are lucky, a diesel will do better, mine with a 450hp detroit does 8-9 mpg.
I don't know the legality issues on seatbelts, I know that if I am not driving I definitely will not be just sitting there, I'll be napping in the back, fixing a sandwich or cleaning up etc. The best way to travel there is in my opinion.