Your desires is what we do and your criteria is close to ours. I'd recommend a Class B as you will find the two Class Cs you are considering will not let you cross the Going to the Sun road in Glacier NP, will be difficult to drive many narrow roads and tunnels you'll encounter, will keep you out of many national monument and national forest campgrounds and will even limit your choice of sites if you can camp. Driving a Class B is a joy. I've heard few claim that with B+ or C no matter what, as it is more a chore to drive, and driving is what you will do most with your criteria. I think I know. I have a 120,000+ plus miles in 8 years with that desire.
There are at least four Class B converters that will do solar panel, four batteries+ setups (Advanced-RV, Sportsmobile, Roadtrek, Great West Vans). Sportsmobile, Advanced-RV and Great West Van will listen to you and customize. Roadtrek just happens to have a four battery solar option. With the rest and most Class C manufacturers you are on your own to customize that option. Leisure Travel Vans, Pleasure-way, Airstream and Winnebago seem to limit you to just what they offer in their catalog checklist of standards and options.
If you think you might snowbird in the winter and hang out for a month or two in a full service RV campground then maybe you are a candidate for a bigger RV. Then you would also be thinking about renting or towing a car.