Many/most Cs are now outfitted with 15K BTU units. Could be a heat pump. Many of the new AC/HP units have lower power consumption than the older 12.5 units.
Many of the C coaches are ducted so you can get by with a single unit as they distribute the air more efficiently.
FWIW. Our Coleman Mach 8 (15+K BTU) cools our 24' View (2 slides) quickly and it maintains the coach in the 70s on a 95+F Texas summer day in the sun. There are three tips. Install clear heat resistant solar film to windows and windshield. Keep sunscreens/shades down on sunny side. (View has Remis style shades in the cab.) Set the AC fan speed on low so the air spends more time on the evap coil. This gets a couple more degrees colder and removes a bit more humidity. Optional to put it on RUN for full time circulation. That will continue to pull cold air off the evaporator for a few extra minutes untill the next compressor cycle.
Note: technically....an RV unit will only produce cold air that is about 15 degrees colder at the duct than at the intake.