Don’t forget the start amp loads can double their running amps, and you have to allow for the starting draw… also don’t forget everything plugged in and turned off has a parasitic draw to it…
and don’t forget any time you are connected to the shore power the converter is always drawing amps in variable amounts…
This is all before the AC, water heater, or microwave is running…
once you are plugged into the shore power you are lucky if you have 18a or 20a left for the things you want to run…
You don’t have 30a to use that you have control over in a 30a system…