I am also an avid cyclist and also use Strava in addition to Training Peaks. I do use the Garmin 520 while cycling instead of the Strava app. The data goes to Garmin Connect and then to Strava and Training Peaks. I use the Fenix 5x for non cycling activity such as walking and kayaking so far and again, the data goes to Garmin Connect and then to Strava and Training Peaks. You do need to grant permission in the Garmin Connect - Account Information to allow the data to pass to Strava. I have not experienced any issues with auto synchronizing my data from the Fenix 5x to Strava. It works great!