The rules don't mention any restrictions regarding the usage of downloaded cars. Are they allowed? Also, are there restrictions regarding the Physics Realism settings? They may affect race outcomes, although I'm not sure about this.
Physics realism is just a setting in-game so I don't see any reason why there'd be restrictions on it, tuning it to personal preference seems like it should be fine imo.
As for downloaded cars, if it's not part of the vanilla game/DLC then that won't be allowed since that falls under file modification, which is p much always banned unless explicitly state otherwise (e.g. some games allow mods to remove RNG).
Alright. I guess only the Red Rocket comes anywhere close to that definition (unfinished by the game devs but added in later by a modder). Thanks for the info!