My $0.02:
Find a good bike shop in a city nearby (probably Yuma or Tucson) and start up a relationship with them. If they can arrange for you to try an e-bike or two that would help you narrow down your choices. There are probably lots of bikes that will work great for you.
Given what you've said about your knowledge of bikes, you probably aren't going to be able to work on derailleurs or disc brakes so I'd recommend getting a name brand bike with a dealer network so as you travel you can have the bike worked on as you need it -- both basic maintenance, any enhancements you decide you'll need, and fixing whatever breaks (and stuff
will break). Another argument for going through a dealer is that given what you want to use the bike for, you'll probably want a rear rack and possibly a front basket -- and getting those things
right is more likely to happen if you work through a dealer.
No matter what you budget on a bike, expect to spend at least $500 on accessories: a decent helmet, a bike lock, some bike bags, and some basic tools can add up quickly. When you are traveling in your RV I'd also recommend bringing a floor pump or a small air compressor (personally I prefer a floor pump).
Also work with your bike shop so you can at least master emergency field repairs like fixing a flat tire. And basic maintenance like cleaning and oiling your bike chain. They should be happy to teach you.
Edit:
I'm going to add that it seems from your description that you are reasonably active and fit. From that I'd conclude that you'll be happier on a decent e-bike from Trek or
Specialized.