My two cents on the option "Highlight Widgets with Focus" (applies to Windows, possibly others).
The simple QSS for showing focus has a certain unpleasant side-effect, which applies primarily to the two widgets: QSpinBox and QComboBox.
Well, the focus overwrites the default 'Fusion' style and ruins the aesthetics of these controls.
The problem has been known for years, but I have not found a simple solution.
Link
I am not in favor of removing this new option if users find it useful, but it is worth adding a note in the documentation that the aesthetics of the UI will suffer with this option enabled. The Accessibility tab is also a good idea.