I tried setting RestrictTeamInvite to “system_admin” as well. If EnableUserCreation is set to true then anyone can add new members. If set to false…no one at all can add members.
RestrictTeamInvite seems to have no effect at all.
-EDIT- With EnableUserCreation set to false the slash command /invite_people -EMAIL_ADDRESS- responds ‘Email Invite(s) sent’ but no email/invite is sent. Should respond ‘Not Allowed’ or some such thing.