In theory you wont notice the difference, only screen tearing if FPS is high enough. However that said your game will appear smoother, as when you experience FPS drops you usually will still be above that 60FPS margin. I wouldn't overclock your monitor either, it isn't design to and it's very risky to do so. Your trying to get more out of the product then it was originally intended for, and it's not like overclocking a CPU or GPU. OC'ing monitors also voids warranty.