Class C Hierarchy List?

With your husband's health and comfort issues, I would consider renting a small Class C or maybe even a van conversion like Roadtrek to assure yourselves that he will be able to travel in comfort. Most Class C's have stiff rear springs to allow for the weight being carried which means that the ride on rough worn cupped concrete higways can be jolting (wherever you sit inside). All flat sided RV's are subject to swaying as big rig trucks pass or crosswinds knock them around. I suspect that short Class C's may be worse in these effects than longer wheelbase RV's. Most major RV makers offer premium models and lower priced models. Premium models may cost $10K+ more than their lower priced models but will have somewhat higher resale value. With the health problems you mentioned possibly getting worse, you may want to sell in a few years.Take your time studying what is available and their features and don't buy on impulse.
Short rigs normally have less comfortable sleeping accomodations requiring setting up and taking down dinette/beds, jacknife couch/beds or climbing up and down ladders in the middle of the night to the overhead bed. Rear bedrooms and RV queen beds are mostly available in 27 foot bumper to bumper and longer rigs.
You won't notice much difference driving and parking a 27 footer vs a 24 footer.
They all require using your mirrors and careful driving changing lanes on freeways, as well as proper use of transmission and speed control on long curving mountain grades.