First off, welcome to the forum, and I wish you good luck with your ideas.
As far as the type of rv, have you driven anything? That is pretty important, as is the fuel costs. Fuel is relatively low now, but it will not stay there. A class C gasser will only get 8 mpg roughly, a B diesel would do a lot better! I think also that the floor plan is the most important consideration that you have to make in either case.
We will occasionally park our rv, lock it up with the generator and a/c running and hit a restaurant or store for a bit while Josie the Beagle sits behind the wheel and listens to the radio. I watch her occasionally with a camera, just for a laugh.
Ohio to Texas is real cool trip, but I can't really comment on the Mexico trip, as I am not qualified to answer. I am sure someone else on this forum could advise you better on that topic, if you search the topic.
If you were my daughter, I would tell you to be safe, not too naive, but remember, most people are really great. There is that 5% that ruins everything for all. Watch out for them!