So after studying the issue for so long I just encountered something that helped me understand what's going on and II might have the final answer. It may not be the answer to all of the issues but I believe most of them yes.
Sadly I do not offer a simple solution.
So what are my findings about: the issues with modern HW and its output are all about not having proper screen refresh timing between the graphics card and the screen itself. Timing and timing algorithms are quite a complex subject and there are many standards. NVidia offers you a chance to set it, you can also completely set your own values from scratch.
Thanks to my recent experience I know that incorrect timing values not only cause exactly the usual symptoms, but they may also cause gradual damage to the display as it interferes with pixel inversion and causes imbalance of pixel usage in one direction (you can look up what pixel inversion is) which further worsens the flickering that the incorrect timing is doing.
I will later write more proof of why this is my conclusion, for now I can only say that thee is no simple solution.
Overall it is not just about the GPU or just about the display. It is about both and most probably also about the rest of the PC as it may have interactions with how the timing is executed. Therefore it is about the COMBINATION of all these components that causes this flickering. Of course, good pixel inversion on the display is the base, but this is the final answer why GPU plays its (significant) role too.
Additionally as timing standards have changed over time this also explains why old monitors usually have more issues with modern HW. You simply need to exchange both, which most of the audience here (including me) are not willing to do as they have their "good" monitors.
And to add more: as the quality of HW is getting lower and lower the pixel inversion is not taken care of very well.
And one extra potential answer: why do different OSes have different impact? I have seen that different colors make this imbalance more visible.
Definitely I KNOW now this is not our imagination nor any serious health condition. It is simply flickering, very subtle, some part of display and some sub pixels only, but it is flickering.