I am now at about 30h of gameplay and it is playable, albeit enraging. I have to switch between deleting the shader cache and restoring it, but I at least found out some fundamentals that get me through up to 2h gameplay easy without a crash.
1. Set post-processing to low
2. turn off strand hair
3. set to fullscreen
4. turn origin offline
5. set veilguard.exe to realtime priority in task manager
6. delete/restore shader cache (change when crashes occurs in 15-30min intervalls (or whenever it annoys you too much))
maybe this helps, until EA gets their collective heads out of their bottomless **bleep**.