Battery self discharge is measured in days at worst, more typically weeks or months. It should not be dropping 5% over the course of an hour or so even if the device is a bit warm. Plus having it plugged in should start charging again once the battery starts dropping too low.

You shouldn’t see the battery drop if it is not using the battery, which is what pass through would suggest.

They changed it recently where you can have two members of a family able to play two different games at ones (or rather number of copies of the game at once).

But that requires different accounts even if one account owns all the games.