ROlling.. Your description of 50 amp service is a bit... Off, but not enough to make it worth correcting.
The important line is this: The adapters take care of everything, be it a 50-30 or a 30-50 or a xx to 15, the adpaters take care of everything.
All you need to remember is to not get Eva Gabor syndrom.. (TV show Green Acres) she could never remember that the generator could only handle so much load so if she plugged in a 6 and a 3 and a 5 bad things happened.
If the "Shore" outlet (house or park) is 20 amps ONE big ticket item provided the batteries have had time to charge.
Big ticket items
A/C, heaters, both space and water.(Other than the RV's propane furnace), Microwave, Vacuum sweeper, Hair dryer, and the converter in some cases if the batteries are hungry.
30 amps: two big ticket items save only on very rare occasions can both be air conditioners (Done it twice, batteries full and fridge on propane water heater off)
50: Generally: All you can eat.