(The forum scales my screenshots, makes them look more blurry, try copying them to your local machine and zoom in 100%)
@Luis Rademacher, I noticed you used 150% DPI on your 4K monitor. You may not want to do that as it will make non DPI aware software look more blurry.
I'm not a computer or math expert, so I could be wrong, but I think for those non DPI aware software, when you set DPI to 100%, 200%, 300%, etc, to scale their UI, operating system only needs to clone original pixels. But when you set DPI somewhere between 100%, 200%, 300%..., OS needs to do some calculates and create fake pixels, makes UI look more blurry. I have tested this many times for non DPI aware programs.