What runs on battery ONLY:
Lights, Fans, Water pump, Furnace, TV (OTA) antenna, Optionally The TV
Motors that move things like Slides or Jacks.
What runs on Gas or 120vac but USES battery power for command and control?
Water heater, Fridge (see note) Air Conditioners
Some fridges are 3-Way, and can run on 12 volt. I DO NOT recommend doing it.
In my coach I have a freezer that is 12 volt (3 amps running) but this is not a standard RV product.. Norcold and Dometic both make ones like it, and at least one model of RV fridge that's all electric,, Runs on 12 or 120 volt.. I do like those. Again 3-4 amps if running on DC. This is in the range of a 2-lamp light fixture.