Windows 10. Parallels 12.2.1. MacOS 10.12.5. MacBook Pro 15" (2017) Retina. Windows looks horrible under Parallels. The setting View > Retina Resolution produces no good or persistent results, regardless of the option Best for Retina Display, or Scaled. The view changes every time I launch the VM. Sometimes the icons are tiny, sometimes huge, sometimes the text in apps is all grainy and unsharp, sometimes perfect. All I want is a view that is the SAME every time I boot Parallels / Windows. Every time. I have no idea what the heck Parallels is playing around with, but it's almost like the VM is randomly configured into a different display situation with every reboot. The ONLY way I've found to get what I want is to turn OFF this "custom scaling" after I boot Windows and then reboot. Doing so produces a good display, but it takes up to 15 minutes for Windows to reboot and settle down. And then the next time I launch the VM, Parallels has gone and f'd with the settings and I have to start over.
Side effect of the unknown changes Parallels makes to Windows settings -- 5 out of 10 times the Windows VM is booted, the taskbar is reset and pinned apps are no longer pinned. Another Parallels bug, it seems.
'Best for Retina display' mode is designed to force Windows to use 200% scaling in order to make scaling fully consistent. Windows should never ever adjust scaling in this mode. You may change view mode to 'Best for external displays'. In this mode, Parallels tools won't interfere with windows scaling at all. There are no changes ever made to taskbar. The glitches you're experiencing may be related to corrupted user profile. Please try to create new user profile.
