for cars i don't have many mods, but i've tried the URD corvette at it looks very nice, also i would sugest the lola t280. I agree with Miroslav, especially on the Virtua_LM tracks, they were very good in rfactor 1 and i've tried mid-ohio in rfactor 2 and it looks as good as in rfactor1 (and i use all of the settings at minimum).
I would also sugest to try the Targa Florio track, i'm not sure were i got them but i think it will be easy to find, and it's very nice