200FPS in COD yes it is possible

You can easily tell the difference between 30, 60 70, 80, 90, and 100hz. You might even be able to place them in ascending order if your eye is sharp. After 100-110 you're getting into the realm of diminishing returns. Back when I had a top of the line NEC CRT monitor I had to run it at 100hz because anything else seemed to flicker. I could take it all the way up to 120hz, but could notice any improvement past 100hz. Maybe if you had two monitors side by side with each refresh rate you could tell, but not by looking at one then the other.

FPS above your monitor's refresh rate is a waste, unless the game is like CLOD and you need that much overhead to stay above your monitor's RR during intense parts.