Blurry UI running VST in Ableton Live 10

That seems… odd. I can’t think of any places where just the presence of the OpenGL module will change the behaviour. Are you sure you aren’t loading an older build of the plug-in with the OpenGLContext attached? Are you cleaning the build folder and completely removing the old plug-in before reloading?

It does sound similar to this issue, which looks like an OpenGL driver issue in Live: