I show the screens in Flatlaf, but in Metal it's the same.

I know that. Only under nimbus and macOS (English) the texts looks better.
A possible solution could be to detect the LaF (like I detect the OS) and instruct the plugin what specific settings to use for the current LaF.(icons, text etc.)

The Axis XYZ disappear in full screen.

I know that also. I've used the default axis provided by SH3D ModelPreview. This wasn't programed for full screen.
A possible solution could be to make my own axis with labels. I will see.
Anyway I remain open to suggestions and pieces of code.