Pro Tools doesn't scale correctly in Windows.
For this reason, its interface is rendered very poorly on high DPI screens. Even experimenting with Windows' high DPI settings, there are several glitchy configurations and only one configuration that makes the interface usable.
I provide two screenshots which explain the problems experienced with 200% scaling on a 4K display.
They show Pro Tools 2018.4 (current version as of today) running on Windows 10 version 1803.
1. With the default scaling behaviour (no custom options set in Windows application compatibility) the PT interface is not scaled at all and looks tiny; the majority of plug-ins scale improperly (I also found one which scales correctly); menus are clipped. The interface is not usable.
2. With the "System (enhanced)" scaling option, the whole PT interface is scaled with pixel-doubling along with all plug-ins (even those supporting scaling). This makes the interface usable, but blurry on high DPI screens. The custom cursors used by Pro Tools are still not scaled and look tiny.