

Gaming is fine, I haven’t noticed any issues but I have to admit that I’m a casual gamer at most. The monitor supports FreeSync and refresh rates up to 165Hz.
I haven’t compared VA to OLED yet, but the latter costs at least twice as much where I live. For me personally, I don’t think that’s worth it. My previous monitor was a Samsung CF791 with Quantum-Dot but honestly I find the iiyama to have nicer colors. That’s highly subjective of course and the CF791 was released roughly 10 years ago, so take this with a grain of salt.
I’ve had great success with restic. It will handle your 4TB just fine, here’s some stats of mine:
Total File Count: 78374 Total Size: 13.324 TiB
and another one, not as large but with lots of files
Total File Count: 1295210 Total Size: 2.717 TiB
Restic will automatically deduplicate your data so your duplicates won’t waste storage at your backup location.
I’ve recently learned about backrest which can serve as a restic UI if you’re not comfortable with the cli, but I haven’t used it myself.
To clean your duplicates at the source I would look into Czkawka as another lemming already suggested.