It's the the human eye has a limit but the problem is making the screen updates match the eye interval, it's not easy so instead you have a bunch more fps on top. My experience is that around 75 it is plenty of additional fps and the eye can't really see much difference anything above that. Over 100 is just showing off your hardware. :P
Anyway rule of thumb is having the fps limit to the screen Hz, I got a 60Hz screen so I cap my fps at 60 too. Anything above is simply rendered in the software but not shown on screen because of hardware limitations.
About the problem, it's caused by the addon trying to compare a number to nothing, not much you can do except wait for a fix. I myself don't use it and last time I checked the code was very hard to read, using a lot of weird variable names, making it hard to debug hehe.
