I would suggest to go with home assistant. I have been running it for couple of years now and I am very happy.
I would also suggest to purchase a Home Assistant Green. While not needed, you can self install on a Pi or a standard pc, it's a small price to support the project and the Green is a nice solid and super stable piece of hardware, I am very happy with it after using first an old laptop, and then a Pi. The green is a clear upgrade from both.
Absutely Endurain. Wanderer has a different focus.
You want endurain I believe.
Its under heavy development but its also quite stable and capable.
Don't give up your Garmin watch, just don't install the garmin app on your phone and download raw data from it like you already do.