I think that the current notification settings are too general, and It would be nice to have more notification options. Some ideas I have are:
per channel notification options
Android (and I think iOS) have notification category that allow for different notification options per message category per app. (An example from the messages app on my android phone.)
More notification options for email (such as disabled, daily, immediately, batched (every x minutes), only for mentions, only for threads i particapte in, all threads, only DM’s)
Per channel notification options
Some of these are implemented site wide and should be easy to bring per user.
I may take a look at the source and see what I can add.