The settings page is split in 4 parts :

1. A general settings part where you can change your locale, currency, timezone and date format
2. Edit the global visibility of your data (see Visibility page)
3. Dark mode activation, you can either activate it permanently or choose hours of activation
4. Features activation / de-activation, here you can deactivate some features. It will remove then from the menu and block access to related pages

All these settings only apply to the current user.