If the primary focus is health with sleep metrics, Oura may be better. Apple Watch is far from the best when it comes to sleep metrics.
And I’d argue that Apple Watch is far from a top contender for fitness too. It lacks a lot of what Garmin, Polar, Wahoo etc. have in terms of tracking. While it is good, I’d look at Garmin, Polar or Wagoo instead.
No. It doesn’t hold the charge to last all day and all night. Garmin does and I’ve previously used that all day and all night but you need to give your wrist some air.
I think the best option is an Oura ring for 24/7 use and Apple Watch for daytime use and exercise.
My experience of the HRV, Vo2 Max stuff on Apple Watch has been hit and miss though. Vo2 Max especially. I’m not quite where I’d expect to be on Apple.