What is monitored and what is not

Have a pair of Watch47 units, have not given wife hers till i figure mine out. What things are monitored 24x7 and what is only discretionarily tracked?

O2 Monitoring - discretionary (damn - wish this was 24x7 if even hourly)
Activity/Motion
Sleep quality (different than activity/motion?)
Heart Rate
HRV (guess that presumes Heart rate)

I see a green LED playing on the wall when I take it off… not having hit any buttons. Some sort of monitoring?

Am android user, though I hope it doesn’t matter. (sorry developers - apple makes its own rules for their customers in walled garden).