Looks like that’s a high refresh monitor with g-sync. Nvidia is known to have issues with that even to this day, especially on super high refresh rate monitors like this one.
The first step to getting a flicker-free experience with nvidia is to get explicit sync support anyway, though. This thread covers the latest state pretty well: Screen Flickering and Tearing with NixOS + Sway + NVIDIA - #8 by ProfDoof
tl;dr is that there finally is a way, but you currently need to use pre-release versions of wlroots and sway (hyprland does not and will never support this as long as it’s a wlroots compositor), in addition to the most newestest nvidia driver, neither of which is available on stable NixOS, so you’ll have to do some work.
Even then, VRR and refresh rates north of 144 still often cause problems, you’ll probably want to create a separate thread if it still doesn’t work after setting up explicit sync.