It would be difficult to give an electrical
lesson through a thread. However I will try. A 12 volt system can be very simple. 2 wires in the circuit. You have a hot wire and a ground. The hot wire is usually the one attached to the terminals on a switch. Think of the British term for a switch, interrupter.
It interrupts the power to the appliance. If you have more than one appliance on a circuit ( very acceptable, your home may have a large room with all of the receptacles and the lights
and a smoke detector on one circuit with one circuit breaker ( arc fault ) in the panel powering it). To determine how much you can put on a circuit you can add up the wattage of each appliance. ohms law will help determine the amperage. Wattage divided by voltage equals amperage. an example with ac current is a hair dryer, typically 1500watts. divide that by 120 volts ( typical
ac voltage) and you get 12.5 amps. The same applies to 12 volt systems. A circuit with many LED lights
is possible and practical. LED Wattage is usually very low as this thread has pointed out. You would use 14 gauge stranded automotive wire for a 15 amp circuit, 12 gauge for a 20 amp circuit,and 10 gauge for for a 30 amp circuit. many of the newer cars are using very small gauge wire for things such as taillights. 16 gauge and even smaller.
As you noticed the higher the gauge number the smaller the wire. 15 four foot flourescent fixtures with 2 35 watt bulbs each will only be 1050 watts.
will not compare with that. You can also use wiremold to run your wires in in areas that have to be exposed. Available in plastic at Home depot and others. My PlayPac has a rub rail around the belly where the two halves come together. Under thee vinyl strip the taillight wires have been run. I have had several Women work on my crew wiring industrial buildings and they did well. So can you! Not rocket science just camper science. a skill acquired is worth its weight