it is possible to configure and save user Media tab with all Use if severity types unchecked (keeping Enabled checkbox checked). As tested, no notification from any source are sent in this case.
1. At least one severity type required to be checked if Enabled is checked;
2. Severity types checkboxes enable/disable media setting (remove Enabled checkbox).
Also, while configuring Media (as well as Permissions) no Frontend element is indicating what user is being configured.