For example, is it possible to hide an ‘advanced’ tab on the page editor for certain users? It strikes me that since it’s called ‘advanced’, then it should only be shown to super users or similar. I’m just not sure how to go about doing this.
Currently it’s not possible, the ACL only controls access to the Config set of pages. Perhaps you can request this functionality in the Admin Plugin issues: https://github.com/getgrav/grav-plugin-admin/issues