The Samsung Health App should use the Android Sleep API for accurate automatic sleep tracking without needing any warable device. Just like the app "Sleep as Android"Who wears wearables during sleep anyway?
I bought an M12 so I was trying to estimate how it'll perform after 3 or 4 years. I think it would work fine for me. I don't generally use any heavy apps anyway, I just chose Samsung because of reliability in my Office like work environment