Hey Stephan,
Thanks for reaching out.
There are some built in features like the email digest function to limit how often notifications are bundled and sent
https://help.ftrack.com/en/articles/1040511-managing-your-account#:~:text=your selected information.-,Include in digest email,-- This setting
and the standard Email notification settings
https://help.ftrack.com/en/articles/1040491-using-notifications
Creating messages and UI notifications is pretty straightforward (see link posted below), but there's not a great way to manipulate who will get notified of a thing. You'd have to examine every update and create event that comes in, then decide whether to send something and to whom.
https://help.ftrack.com/en/articles/1040465-actions
Erik