I have had an 2070 Super until just 2 months ago, when I switched to a 2080 Super. I play at 1440p @ 144Hz.
The 2070 Super had plenty of perrformance, I never felt like it was lacking in performance or missed out on something better - it was an excellent GPU, and I'm confident you would be very satisfied.
While I have seen a minor bump in FPS, the 2080 Super - as expected - don't feel like much of an upgrade.
I bought the 2080 Super "just because", I didn't have any particular reason for it, and I was fully aware that it was a lot of money for only a few FPS more. I have not regretted my purchase, however.
But I'd say the 2070 Super offers plenty of performance for 1440p gaming up to 144Hz. If you want the 2080 Super it is also a...