FPS gain is the aime of the mod. It's removing 'useless' objects > means reduces the polygon count > means better performance.
Installed it yesterday, runs fine so far, but only drove Nordschleife, you may know why ...
If you backup your tracks folder ( in pakfiles folder ) you can easily roll back, without reinstalling the game, if you notice some issues.
Sometimes not loading tracks properly can also have other reasons.
Some reported problems with loading diffrent tracks while using totally unmodded game.
BTW; if you running a real good machine with fine FPS count on high, there's no need to use this mod!