I had garmin watches and still using Garmin (Edge, cycling computers) along my Apple Watch Ultra.
For you combining from Garmin, what you will miss is the out of the box data analysis which Garmin Connect does. It’s not a matter of data, data is there, only the Apple health app is mysterious.
I would suggest picking up some third party apps such as
Athlytic (https://www.athlyticapp.com/) Heart Analyser (https://9to5mac.com/2023/04/18/heart-analyzer-apple-watch-iphone/)
That being said, the Apple Watch is galaxies above Garmin in nearly all aspects… especially apps, usability, integration, the list is endless.
Personally, I would say if you’re not hiking away for weeks with no access to power and really needing your watch, or a triathlete, go directly to Apple Watch.
My AWU is actually suited to any circumstance.
For office and formal ones, I swap the band to a titanium one and the watch face to a simple California