Also, I've not tested using my capture card without obs, so i'm not able to say much about that...

but either way, I figured out that i can get rid of the noise by turning the volume up or down on the audio mix destribution thingy until the noise are gone and then adjusting the volume on my PC and switch/monitor to still get the same volume

And I had some trouble with weird noises in the background (could be a problem specifically to my system tho. I only experienced it thru my pc out, and the headphones slot of my switch not while useing the monitor out [and I already had that problem with my PC audio out before])

My current setup, which I'm very happy with, looks something like this:

Be aware, if you use the headphones slot of your switch, you're not gona have audio on your capture card, so gl if your Monitor doesn't have an aux out lol
(you can ofc find other workarounds with splitters, etc.)