I just got a 1440p 144hz G-sync "TN" screen. TN has a fast response rate, but doesn't look quite as good as "IPS", although I spent $420 on cyber monday for mine, while a good IPS screen is going to cost a lot more. Also my GTX 1070 and FX-8350 does a pretty good job of running most games at the full 144hz at 1440p, although I have to turn the settings down a little.
Also one game I was playing was locked at 60hz, and it was kind of jittery, so I'm glad I didn't get a 4k 60hz screen. Also it's 24 inches, usually bigger is better.