User Notification Settings: change default settings and modify in bulk

Hello

I have some questions regarding space notification messages (such as Comment/New Content/Deleted/Membership in /user/$uid/settings )

Is it possible to set a global default for the selection of these notifications when any user joins any space?

Is it possible to bulk edit users' notifications preferences, perhaps on a per-space basis?

I'm guessing the first, the global default, could be pulled off with code invoking some sort of hook, but I'm at a loss to know what that might be or what settings I'd have to alter.

The second could probably be done in one-off fashion via SQL but I'd like to know if it is possible to build a view capable of editing users' notification preferences.

Thanks