I think the way to do this is in iOS itself. I would be shocked if Coros has better notifications tech than Garmin; it’s a way smaller company. I don’t even remember touching notifications when I set up my Coros watch. I think it is just governed by my iOS settings.

iOS has a lot of power to finely control notifications. For example for Slack I just have app badges, while iMessage buzzes. In Mail, only people I’ve added to a small “VIP” list cause a buzz. Otherwise I just look at the Mail app badge to see how many emails have come in.

It takes time to tune it, but it is a very good investment IMO.