I used to own an "ASUS RoG Strix RTX 2070 Super Advanced Edition", and I used it for 1440p @ 144Hz gaming, and that seemed to be a perfect match for both high FPS and 1440p, with high quality visual settings in-game as well.
I later upgraded to an "ASUS RoG Strix RTX 2080 Super OC Edition" which I currently use for the same 1440p, 144Hz monitor, and while I did see a few more FPS, it is not really anything I noticed unless I really paid attention to it or ran a benchmark.
The performance increase of the RTX 2080 Super, does not justify the extra cost, in my opinion (having owned both cards), if you look at price vs performance at 1440p.
I did not upgrade because I felt like I lacked performance, it was a purely because I was offered a very good deal.
For 4K though, I'd go for the 2080 Super.