Anyone run a Paid Community? How do you monitor community health?

Doing some exploration into paid communities! Would love to know -

1. What metrics do you monitor (or have tried to monitor) when thinking about your Slack community health / engagement? Ex - slack messages sent, links clicked, network graphs etc.

2. Have you previously encountered low engagement users that you felt were at risk to churn? Curious how you knew this and what you may have tried to engage them?