Update since I tested some things and still need assistance:
No flickering in Davinci Resolve 17, HitFilm. Flickering in Premiere, Photoshop, After Effect, Audition.
Game wise, no flickering in FFXIV, Death Stranding, Witcher 3. Flickering in Path of Exile, GW2, Cyberpunk 2077.
I really cannot find a solution and GPU doesn't seem to be the main issue.