Sarah, to get to the point on one question you asked, "What is OCCC?". All Ford E450 chassis, made in the last few years, can carry a max load of 14500 pounds (GVWR). The difference between the weight of the motor home and all its appliances and options like slide outs, leveling jacks, subtracted from the GVWR equals the amount of weight of people, food, fluids, clothes, and stuff you can carry. For motorhomes, Class A & B included, its not the "room" you have for stuff, but the weight of that stuff that matters.
For short, or local trips, you might not need to carry a lot of stuff. But, for longer trips, or trips spanning lots of time (Snowbirding, or full-timing), you likely will need to carry more stuff, thus requiring a rig with a higher OCCC. This number should be posted in the rig somewhere if a new unit. Do not depend on the sales rep to provide you with accurate info on this. Ask to see the OCCC label or do your own research.
As an example, our Class C has an OCCC of slightly over 2900 pounds. Even on our longest trips (Alaska, 2 transcontinental trips), we have not been near our capacity including four adults. By contrast, at a large RV show a few years ago, we were in a few Class A rigs that would have been overweight with only our family of four on board, no food, water, stuff.
Generally, a shorter Class C has a larger OCCC. Good luck with your search.