The purpose of this article is to provide insight into a common cause behind the freezing when changing material property values and give practical steps to resolve this issue.
The GIF below shows the slowness/freezing when adjusting the Level/Roughness values, whether increasing or decreasing it:
The cause of this freezing is a high viewport image and texture resolution. In order to get rid of the freezing, go to Configure Viewports > Viewports Configuration > Display Performance and lower the Maximum, for example to 512x512x512:
The freezing/slowness should be gone now:
Note: If you change your images and textures resolutions to very low values, the texture display quality in the viewport will become much worse. If you wish to keep high quality textures in the viewport and get good performance at the same time, you will need to find optimal values for images and textures resolutions.