"But seriously, I've read enough old posts to understand what a converter does, and I'm wondering if we even need one? I suspect we won't plug in much, but if we did do you have to have a converter? Or can you plug in for the 110V side and use the battery for the 12V stuff at the same time?"
It's all very possible....I got rid of my converter two years ago (kept the breaker panel and fuse panel)...bought a good three stage charger....when I plug in the charger comes on....all twelve volt power comes from the batteries all the time...(no power from the TV)....seems to work just fine
(the fan on the charger was a little noisy so I swapped it out for a quiet computer fan and enlarged the vent openeings)
as somebody said a stove top toaster works just fine...and takes up less space... getting rid of the converter "created" new usable space....my new charger weighs less than half what the converter did.....and that is what IT is all about ain't it.....space and weight