Reported as a legit bug still waiting hopefully will be fixed soon. Hard to believe QA team don't find those bugs right away...
@DavideOC Unfortunately, I can only share what the Kontakt team shared that my colleague already shared to you: "According to the developers this behaviour is to be expected with Kontakt 7. Generally it's supposed that you want to have the UI in more or less the same physical size (in cm). E.g. if you have a hi-res (200%) display, you don't want to have your UI twice as small. Therefore this slight blurriness is to be expected."