Well I am not versed in motorhome wiring but I will be wiring the bus based on code for a house. You can get up to 6 recept on a circuit. so really you can probably wire the whole bus on 2 or 3 circuits. All of my lighting will be 12v DC. Most likely LED to keep the current draw down plus it is already wired for it in the ceiling.
As far as the breaker panel I would recommend you buy arc fault breakers for each recept circuit. They are more expensive than a regular breaker but it is cheaper than buying a bunch of GFIC recepts. Grounding is very important on a vehicle because you don't have a good earth ground since you are isolated on tires. If you are on Shore power you will have a ground supplied from the power supply. But if you are on Gennie power, you rely on the GFIC's to protect you. Unless you drive a ground rod when you are parked (who's going to do that, right).
Wiring a breaker panel is very simple. Keep it clean that way you don't get confused. Wire one circuit at a time, landing the ground to the ground bar and then the neutral (white) to the neutral bar (there should be a bonding bar that connects the neutral bar to the ground bar.) If you are using the arc fault breakers, the breaker will have a white pig tail that lands on the neutral bar the the white wire from the romex will land on the breaker. Then connect the black wire to the breaker. I know this sounds confusing but it will make sence once you look at it.
LOL. Yes there is a HUGE difference between a electricain and a electrical engineer much less, a mechanical engineer.
Good luck. I'll be here if you need me