Re 12 volt lights:

Every single room, including the engine rooms and generator room, on my 1965 boat has both 120v and 12v lighting. Generally the overhead room lights are 120, while the reading lamps over each bed are 12. Each head has two sets of switches, with two lamps. Hatteras designed her with totally redundant systems. We lose the luxuries if the generator quits, but all the important stuff (fresh water, toilets) runs 12. I added the inverter to keep the fridge cool--have not been so spoiled as to add the ice maker yet.