Ehrm correct me if I'm wrong but do you think that because your screen has 144 mhz you're gonna reach 144 fps ingame? I can t see how that even has anything to do with each other.
I have the Asus Rog 27" with g-synk and a 980 Ti, and usually have an fps between 140 up to 190 depending on density.
so I dont think that it is your monitor that is the problem, I play in 4K res 3680x2140x144 mhz.
www.twitch.tv/hayabusa73 feel free to stop by and say hello when I'm live