Just my opinion, but 20ms is not significant for anything other than very high-level CSGO or fighting games. For example, the good old Dell U2412M had 17ms input lag and many of us gamed on those for years without complaint. Even the well-regarded Eizo FG2421 had 10ms of input lag + 4ms of pixel response time to deal with. Outside of very specific game scenarios played by highly sensitive people, anything below 25ms is fine. It's 30-50ms+ when it starts to get really noticeable even for average games and mildly irritating.
All of this assumes that the 20ms ballpark is correct, of course.
I agree. My PG278Q has a response time of 1ms and input lag well under 10ms and I can't really tell that much of a difference to my Samsung KS8000 with much higher response time and input lag. In short I enjoy playing games on both of them but while I do play games that require accurate timing (e.g. Dark Souls), I don't play competitive FPS or fighting games. While I would prefer as low input lag as possible as well as minimal response times, TVs generally tend to be worse about this and seems OLED hasn't quite caught up with LCDs in the input lag department.
Ultimately I would like more effort spent on backlight flickering solutions as those do a lot more for motion clarity than shaving off a few ms off response time.