My strategy here is to default notifications off for everything other than calls and texts.
And then manually open Gmail to check mail, manually open Instagram when I feel like checking notifications, etc.
It’s such a better experience when you’re opening an app because you want to, and not because a notification is baiting you.
I actually have an Apple Watch that I mostly use for hiking. I just use a $30 Timex most of the time that I don't need to charge.
iOS or Android?
Can you default it to off and not have any popups (during run/install) asking you to enable permissions to notify? Or do you have to decline once per app?
Allowing GMail to only show a notification when an email is categorized as "important" is an acceptable compromise. (Setting up a bunch of filters to manually control the "importance" helps a lot, too.)