I think 2K is 1440p and 4K is 2160p. If you go on any monitor website or Newegg and click on 2K, it will give you 2560 x 1440. 4K is 3840 x 2160. It’s based off the horizontal resolution not vertical.
That’s actually a good idea. A lot of HDR monitors and Windows sucks when it comes to 10-bit support and HDR. I have thought about getting a new HDTV since my Sony 1080p HDTV is an LCD and 10 years old. I think I’m going to go with the high refresh rate 1440p monitor since it will be more reasonable for my graphics card which is 1070.