Fractional scaling or --scale on one monitor affects the other monitor
Solution 1:
This is a known problem of using scaling on Xorg, but you cannot switch to Wayland because you are using Nvidia drivers.
Try the solution mentioned here: https://www.lguruprasad.in/blog/2020/01/13/how-to-get-a-dual-monitor-setup-with-mixed-dpi-working-on-xorg/
The trick is to apply some sort of ‘upscale’ to the lower resolution monitor.