In download section there is reshade and sweetfx : 2 different plugins which modify display rendering.
You can also try GemFx.
I prefer enbseries hdr plugin rendering but big fps drop under rain because it was never optimized for GTR2 : originally designed for GTA and recent versions are flickering with GTR2.
You can also enable DSR if you've got a nvidia card.
GTR2 is a 13 years old dx9 game so you just cannot compare graphics with modern dx11/12 games such as Pcars/ACC/rf2
This is vanilla game (+ map plugin and PnG HUD) at 4xSSAA & 16xAF by using a Radeon Settings custom game profile. I don't think it's that far behind RF2 graphics and the loading times are much quicker. I haven't installed any visual upgrade mods because it runs very well as it is and looks more than good enough for me.