I wrote one of the guys, didnt got a feedback, so i tried something new.
I changed the unmanic workflow to the following:
What i changed was AAC instead of AC3 and i remux (change format to .mp4) and then encode to 265. Im currently converting 70tb of stuff to this format.
All movies i tested so far work now in ORIGINAL QUALITY and even in TRANSCODE via NVIDIA. Before it was JUST encode to 265 and output mkv.
NewDisplayName's post in Transcode / direct play Plex im sick of it, ill pay for help was marked as the answer