Solved Everything got re-sized when I set my PC to Duplicate mode

*****EDIT*****
Long story short:
I set my PC to duplicate mode with my main monitor and my TV.
For some reason it resized everything on my PC in the strangest ways and I couldn't get it back to normal.

I tried restarting my PC a few times, and disabling everything but my main monitor, but that didn't do anything.
But now after I wrote a huge post here with tons of details, I DISCONNECTED everything but my main monitor completely, and restarted again. And THAT worked.

So it's finally back to normal and all the time it took me to take proper screenshots and explain the issue as detailed as possible was a total waste of time...