Hey there,
This article should help you out:
As well as this forum thread:
The main benefit is that these rides will stay on your TR Calendar and automatically replace existing sessions that may have previously overlapped with your Group/Solo Rides. For example, if a hard group ride fell on the same day as a hard interval session, you’d have to manually delete the hard interval session. Now, Plan Builder/AT takes care of that extra step. 
The rides you do that sync via Strava should pair up with any Solo/Group Rides you have on your TR Calendar.
Hope that clears things up – let me know if you have any additional questions!