Final question--so my Garmin will read atmospheric pressures, Garmin Connect will fix it based on topographical maps, then what happens when it goes to Strava? Will Strava take the corrected number or come up with its own?

The only reason I use Garmin Connect is to interface with Strava. Garmin Connect totals always differ a little bit from Strava on the same ride. I imagine they interpret the gps download with different algorithms.