The Subscription settings currently have only two parts, one specifying who can change them when someone is automatically added, and one specifying who can modify subscriptions.
The Subscription settings are configured on each user account as to what they want to be automatically subscribed to. The setting related to who can modify those is either "Administrator", meaning only an administrator can modify any subscription settings for what users are subscribed to, or "User" meaning all users can modify their own subscription settings.
Most of our users are not trusted enough to modify their own subscription settings, so we're currently using "Administrator" for the restriction, but we have a collection of Senior Developers and Project Leads that need/want to be subscribed to a number of different things and are trusted enough to modify their own subscription settings. The only solution is to currently make those trusted users Administrators, or to have one of the existing Administrators modify the user's settings whenever they need/want to change their subscriptions.