That was the problem I mentioned regarding the scaling of the video. In VLC this was easy to fix -> see article. For in-browser videos like youtube all was fine without a config.
The main problem I have is graphics artifacts in applications that use webkit, for example Vivaldi and Code.
Here(https://gfycat.com/MemorableIndolentDuckling) is a screengrab I made of the tearing, it mainly happens when I move the mouse over certain objects. Everything works fine in firefox so its pretty weird.