Edit the following values on your .PLR userdata file
Max Headlights="3" // Max headlights visible relative to your car.
Headlights On Cars="0" // Headlights illuminate other cars.
Shadows In TV Cockpit="0" // Disable/enable shadows on cockpit
Explanation:
Max Headlights: Limits the number of proyector lights used by cars, saving a lot GPU Usage
Headlights on Cars: Enables/Disables proyector Headlights being affected to other cars (Saving GPU Usage)
Shadows In TV Cockpit: Enables/Disables shadows on cockpit.
Also to prevent crashing, play as windowed mode.
IF you want fullscreen-like experience, use Borderless Gaming to play as borderless windowed (it's fullscreen but not at all). Also helps you to alt+tab safe.
and use +fullproc -highprio on your rFactor shortcut properties, at the end of "Target" after "" and space.