I have just tried the Garmin product (vivoactive 5) after a few years using a Fitbit. I am highly confused with the "recommended sleep" because it doesn't adjust when I take long naps during the day. I was excited when I saw the options to balance sleep with daily output. I think it's a great idea if it worked. Perhaps, Garmin is already working on fixing this?
It would be a good idea to add the ability to adjust the sleep input either by autodetection of naps (like Fitbit does) or at least a manual option to adjust input.