The vast majority of what you're running from RV DC are things like lights, fans, phone chargers, and other cigarette-plug-adapter type devices. My RV has a 12V DC fridge. For anything more - particularly air conditioning - you need AC for sure.
My inverter-charger is connected to my batteries with 4/0 cable. That wasn't fun to run.
My inverter-charger is connected to my batteries with 4/0 cable. That wasn't fun to run.