I don't see a need for 120v for the camping we do. Mostly because there is no AC power where we like to camp. But for us we need 12v, mostly for LED lights, the roof fan, and most important to charge all the devices, phones (used for Nav and camera mostly), iPads, cameras, com radio. I'm sure I missed a few other batteries that need to be charged. I would at least run a few wires to some 12v cigarette style plugs and you can use the USB adapters with them. Plus a simple cabin and galley LED light. You can probably get away with a 35 or 50 amp-hour battery.
I got this light for the cabin and really like it. Dims low and is more than bright enough.
https://www.amazon.com/gp/product/B06ZZ ... UTF8&psc=1