I did some more testing and am close to giving up that there will be a fix very soon...
Short summary, the screen tears, flickering, scrambling, display errors happen randomly and cannot be directly forced. Apparently, when deinstalling the Intel Xe Iris driver all the flickerings etc are gone, but also all screen adjustment features, eg 120Hz, HDR, night time, adaptive lighting etc. They are happening more often whenever there is more going on on the screen, eg youtube/netflix videos, lighting change effects and animations albei still random.
I did not find any way to reproduce them reliably and the shape and coloring of the screen flickers, tears and scrambles is also not always the same.
I tried recording the flickers with a screen recording software. I figured out that the flickers are appearing on the physical screen but apparently not on the video recordings! Not a single video I took had flickers in them and I took like ten with personally confirmed flickers. The only other explanation I could come up with, is that the flickers hide on frames that weren't recorded, ie I recorded with less than 120Hz. (I will try to repead the flickers on lower Hz and try to record everything frame perfect but statistics already tells me that it is suspicious that not a single flickering was recorded properly despite having a large sample size...).
I would really like that MS would acknowledge the issue and would have a look themselves what is going on on the affected devices. It might not be MS fault but Intels considering it apparently only happens when the official Intel driver is installed and not when the MS backup driver is used.