Here is the answer to your dome light question. There is a switch at the dome lights that will turn them off so when you open the door they will not turn on. If you leave that switch in the on position and so when the door opens they come on then you can do this. Let the courtesy light timer wind down so the lights turn off while you are sitting in the drivers seat, then reach down with your left hand and rotate the dash dimmer switch all the way up until you feel it click and look at your dome lights, they are on. The confusion is because the on off switch between the dome lights.
The switch below the radio is for the starting battery or coach batteries, so when your parked you can listen to the radio off of your house batteries. This was spec'd by the original owner of my PC and then adopted for follow on coaches I believe, so late in 2017 I believe it became standard...
Hope that helps and happy travels!
