It looks like there are some issues with 120Hz refresh vs 144Hz refresh on this driver still.
When selecting 120Hz for your refresh rate you lose the colour output format "RGB" and "YCbCr444" instead you only get the option "YCbCr422" which shows image corruption on Driver 446.14 all 3 options are present.
I wouldn't have an issue with using "YCbCR422" however it causes a lot of image corruption. "RGB" is the default setting which is not present when selecting 120Hz
Reproduction steps:
1. Install driver 456.55
2. Open nvidia control panel under "change resolution"
3. Select your native monitor resolution + 120Hz (must have 144Hz monitor)
4. After hitting apply notice that the "Output colour format has changed from RGB to YCbCr422.
5. Select nvidia settings and try and change the Output colour format option notice you no longer have any other option other than YCbCr422.