OK so i just tested Just Cause 2 ,
In Performance mode the game loaded up quickly like way too quickly.
No Fps drops. In start i got 63 fps while in quality i got 60 , when i moved to jungle i got upto 75 fps while in quality i got 54 fps , and i felt the fps.
I really didnt see any quality loss and i did took pictures in which i saw no differnece