Out of the box I would have EMS triggering on any _error_ (not warning/info) for any Unity component. There's a class in the EMS setup just for this. It's already smart ennough not to trigger too many notifications to a single target (i.e. a batch of errors all plop in the log at the same time - that's only going to generate a single notification event).
If you find error messages you don't want to hear about, you can explicitly exclude them (or exlude all messages from that particular component if you wish).
Not sure this is official "best practice", but it's how we designed the tool to be used.
