How exactly the cables are laid in your caravan | motorhome depends on the respective model and the floor plan. However, they all have in common that the cables for 12 V and 230 V must be laid completely separately. Likewise, there are separate fuses for both voltages in the caravan | motorhome. Most devices are designed for 12 V when camping. They get their electricity from a central distributor. All appliances should have their own fuses in the motorhome. It is always advisable to have spare fuses with you in case one breaks.
The distributor is usually located on the EBL (electrical block) together with the charger, isolating relay and refrigerator relay. Most 12V consumers are also fused there. A common place for the 230V fuse box and other electrics is in the wardrobe, under a bench seat, the kitchen unit or even in the vehicle floor. In addition, there should be multiple replacements for all fuses that are needed!