Cantabile build 3662 introduces a new feature that let's you control how plugin GUI's are up-scaled on hi-dpi monitors.  

Previously this was an all or nothing option but a new setting now allows this to be controlled on a per-plugin basis.  For plugins that support it, crisp hi-resolution GUI's are now possible while also allowing for legacy (blurry) up-scaling for plugins that don't.

This video walks through the new setting and when you might want to use it: