I left off a few mods you should get.
Shaders Patch - Dynamic Lights
This will make headlights work and look great at night on the right tracks. Tracks with night versions are the best one's to use for nighttime racing. You just need to change the start time of your race in Content Manager to be starting at night (I missed that key aspect on my first attempt).
https://acstuff.ru/f/d/28-shaders-patch-dynamic-lights
Assetto By Night
I'm not sure you even need this once you have Sol and Dynamic Lights, but I grabbed it anyway and it's pretty cool. I mainly use Sol.
https://www.racedepartment.com/downloads/assettobynight.20364/