I've used Apple watches for several years to monitor sleep (now have a series 9).
Monitor heart rate, sleep quality, SP02, respiration etc.
It does tend to temper alcohol use - just a couple glasses of red wine result in zero deep sleep and increased heart rate throughout the night.
SP02 and respiration were indicative of a lung disease which I'm being treated for.
I've used AutoSleep for years - works great.
You can tweak it to most accurately record the time you're in bed and how much is awake, light sleep, moderate sleep, deep sleep. It will automatically record a nap if I happen to take one during the day.
I usually charge my watch in the morning while having coffee and showering. It is on my wrist at all other times.