I thought I should share my experiences of syncing Strava with Garmin Connect. I have always used starred segments in Strava and have also set Goals where possible. These were seamlessly transferred to my Garmin Edge 520.
However once I reached my 100 segment limit in Garmin Connect I had some unexpected results. If I unstarred segments but left the Goal in place it seems as though the segment was still counting towards the 100 segment limit but just not visible on my 520. Some segments could be starred / unstarred and would sync accordingly but others would not. If I deleted all the segments from my 520 and disconnected Strava from Connect on re-connecting I could see a number of currently starred segments as well as some segments that used to be starred (but were currently Goals). The solution was to remove all Goals which did not tie up with starred segments - not a great loss.
I conclude that starred Strava segments and Strava segments with goals both contribute to the 100 segment limit and may drive you nuts if my experience is anything to go by. If anybody has other theories I would be interested.