Mark,

Should the photo notification setting be separate from the album
notification setting? My gut says no, but want to make sure.

I'll go with your gut. Also for File folders.

Also, I forgot database notifications, which don't exist anywhere
right now. Would you want to know when a row was added, or just when a
database was created?

I concur with others' comments: both row and table.

My thinking with aggregation is that when an email notification is
generated, I'll wait N minutes to send it out to see if any
additional, similar email notifications are generated. If so, I'll
combine them.

I still have concerns about timeliness, but maybe it isn't such a big deal that I should worry about first-one-out delay.
https://beta.groups.io/g/main/message/25395

But it suddenly occurs to me that moderator notices (such as member/message approval) should not be aggregated, under any scheme.

And since every exception deserves an exception perhaps retain the one for Direct Add: only one notice need be generated (to the other moderators), not a "member joined" per address.

Or maybe "member joined" generally. Acceptance of an invitations if a mod sent out hundreds, or other mass-marketing of the group, could cause a flood. None of the rest seem like they should plausibly need aggregation.

Shal