1 Settings to reduce loading lags
"Texture resolution scenery" and "Rear scenery" - affects the VRAM heavily
"Terrain detail" - affects the VRAM and the RAM
2 Settings which affect the fps
"Max visibility buildings, trees, rest"
"Trees in 3d from"
"Maximum visibility AI vehicles and AI people"
"Visibility factor rear view mirror"
"Parallax mapping"
"Calculate detailed lights"
"Inside and outside lights" - differance between day and night, espacially headlights
"Show shadows"
"Enlight particles"
"Enlight windows"
"Realtime reflections"
"Post rendering effects"
"Reduced meshes for own vehicle, own train, or AI vehicles"
3 Settings with small effects on loading lags
"Maximum object visibility" - if there are many different objects on the map
"Texture resolution for own vehicle" - affects the VRAM more than the loading lags
4 Settings with small effects on the fps
Highest object visibility - if there are tons of objects on the map
"Per pixel lighting"
"Shining surfaces"
"Use normal maps
"Shadow resolution"
"Blur shadows"
"Realtime rain"
"Antialiasing"
5 Comparison for the settings that affect the simulation a lot
State zero - A screenshot when using the graphic presetting "Don't do it!" - the reduction begins at this setting!
Terrain detail on "high" and "low"
(You see no difference, right? The terrain detail affects mountains and so on. When simulating cities you can reduce this setting!)
Maximum object visibility for buildings (3000 - 500), trees (2000 - 100) and rest (1000 - 225)
Trees in 3d "far - off"
Calculate detailed lights "on - off"
Inside light and outside light at night "8 - 4"
Headlights at night "8 - 1"
Show shadows "on - off"
---
Thanks to the München-Addon to provide the screenshots! 
The vehicle is the GT6N from the base content, not the R2.2b from the munich addon.
