I read on this forum that a k4200 is safe. However the one I had and later returned did not change the pixel flicker on the monitor side under the microscope. I was also using displayport, and trying novideo_srgb and ColorControl to try to disable the dithering. Of course, if I am measuring pixel inversion and one is sensitive to that, then the problem lies on the monitor side and changing the gpu would not help.
In your situation, would another solution be simply using a high refresh external monitor like the lg or the portable monitor work connected to whatever computer of your choice as long as the computer can drive the monitor at desired refresh rate?
This another forum member's pixel inversion video. The flickering is different from what I captured using the microscope and high speed camera.
Just adding this for reference: pixel inversion easily confused with temporal dithering and vice versa: