I noticed that instead of having both tail lights connected to a switch, they are separated, does anyone know what side I'm supposed to use when running light Loco, or does it matter.
A single one would do in BR days. Some loco types had a single 3 way switch, centre being the Off position, and the other positions one for the left tail and one for the right, so you could only have one or the other on. I also don't think it mattered which one was used.
I believe that's correct: light loco or a full train, as long as there was a red light "at the rear" you were good.