Hi,
My "break out box" is a bit different. I have a 30 on one leg and two 20ties on the other leg. They each have their own breaker.
My wiring changes inside the rv are plug and play as well. I used male plugs for the converter and water heater. I used female plugs for the auxiliary shore power cords. This gives me a maximum of 30 plus 20 plus 15. I added additional outlets to each auxiliary shore power cord so in winter time I can run a lot of extra electric heat.
The nicest part is that when there are multiple 15 amp circuits available (Church parking lot), I can have 45 amps to use.
It takes me 20 seconds to move from modified to OEM for the wiring.