For each Discourse site I use, I set up my Notification preferences (/my/preferences/notifications) to the following:
Being liked is nice, being notified is a bit distracting.
Even when I’m active on a site, I want bounds on how much I’m being drawn to it.
If the site uses Assignments, setting the frequency of the reminder messages is useful.
Another panel of settings to check is (/my/preferences/emails), as that will greatly reduce received email:
I hope those provide some assistance. 