I am not sure what you can do without an account, because I created an account on day 1.

It connects to the phone over Bluetooth. Many operations need your phone to have internet. There is a kind of primitive app platform. The only app I really use is for Home Assistant, it makes https requests to HA over the phone. I connected it to Strava too, it can realtime send heart rate to that app without going to the internet, but it required jumping a few hoops in settings.

Thank you. This is useful to me. I will look into it more closely, but I think that will likely not be for me.