I think the only apps I have currently giving me notifications that aren't permanent or semi-permanent notifications (netguard, browser, and my local music player app) are my calendar, messaging app, and a single game. I refuse to let either the number of open apps and notifications on my device pile up to more than maybe 5 each, max.
If a notification sends me an ad, I will block the app and also review whether I even need it. Anyone willing to shovel ads at me in my notifications is not my friend.
Other stuff is simple:
If I need to know the information right away I allow a notification. Stuff like calls, messages, server monitoring, security, etc. Notifications that only fire when actively using or just after using an app also get to stay on if they are useful.
If it's not urgent, I set a reminder in my to do list to review it on a recurring basis, for example "check Mastadon, weekly, Saturday"
Follow up question: how do you handle apps that have persistent notifications?
Most apps with persistent notifications that I used allowed you to turn off that notification in the app's settings. Others utilize androids notification category management to allow you to disable the persistent notification.
Phone is on vibrate all the time. Signal only, but also have Pushbullet set up so I can send notifications when new movies/tv show episodes are downloaded and added to my Jellyfin.
Like yourself, SMS and phone calls. My bank app also handles authentication of online purchases a bit better with notifications enabled. Everything else is disabled.
On desktop I have notifications for email as well as those mentioned above.
Sms, calls, discord, Google voice, work emails (I rarely get a work email...maybe a couple of times per month)
I have my personal Gmail to get silent notifications so I know if something happened but I'm not repeatedly spammed.
Most other things are off unless they are unobtrusive. Ex: my robot vacuum stays enabled for notifications so I know when it is done cleaning, Uber eats is enabled for order tracking but disabled for promotions