Hey Primus, thanks for the feedback, always appreciated!
For the group ride, every rider will have a fit file after the workout (saved in the History folder).
You can do a test ride to see how it works.
Strava upload only work for solo usage, it is not supported for club mode since saving the credentials for each user would be complicated. You can share the History folder on a sharing service like Dropbox so all users can retrieve their workouts history when they want.
Let me know if you have any other questions.