Concerning racks, if you remove the battery, the bike isn't much heavier than an ordinary bike, so any rack should work. Mine are only 10 pounds heavier than before I electrified them, with the battery removed. But I prefer a hitch-mounted rack that supports the bike from the bottom, like my Swagman, and I wouldn't trust any bike to one of those ladder-mounted racks. One thing to consider, although 10 pounds probably won't overload your carrier, it's enough to make two bikes more difficult to lift onto a carrier that's mounted up high on the RV.
I'm still experimenting with the range on my kit-built ebike. It's amazing what a difference NOT using the throttle makes! Yesterday I charged it to 100% and took a 15 mile ride in "assist level 2" (of five!), pedaling all the way. It feels a little foolish because you're just making the pedals go around. It doesn't feel like you're actually contributing any energy at all, but apparently you are. I averaged 19.5 mph for the ride (according to the computer) but only used 10% of the battery! That extrapolates to 150 miles, which can't possibly be accurate. But to put it in context, I've previously run it from 100% to 0% in 20 miles, on the throttle alone. Maybe because it's tough to keep it under 20 mph when you're riding it like a motorcycle.
Even though you're not working very hard, just making the pedals go around is a workout, after awhile. So I would advise choosing a bike that has a throttle (many don't), just so you can take a break now and then. But for the sake of range, you should probably not expect to use it all the time on throttle alone.
These things are a lot of fun. I'm looking forward to trying them out on an actual RV trip.