Currently, it does not appear to be possible to adjust the following aspects of the login screen through Settings (Gnome 49):
- Display layout
- Display resolution
- Display rotation
- Choosing the primary display
- Background image
I think it makes sense to add options to adjust this to the Settings application. Or, to allow for an option (like a button) to synchronize the settings of an administrator’s logged in session to the login session.
The choice of primary display, layout and rotation is especially relevant for people using multi-monitor setups, possibly in combination with rotated displays.