I loved my Gear S3 hardware wise - but I much preferred Android Wear software wise.
I have a Fitbit Ionic at the moment (don’t laugh). It’s still by far the best fitness app out. That’s as far as the phone side of things goes - and the user base (so you can link up with friends and stuff, because everyone has one).
I have seen screenshots of the refreshed Google fit though and it looks very promising.