Compacting soil after removing fence posts to install new posts with vibratory ram?
Cut off old posts slightly below grade.

Leave concrete footing in place.
 Drive in new posts 4feet deep into ground at a short distance to the left or right of old post. Driving in that deep would mean no footing necessary. Leaving the old post base and concrete would eliminate need to compact.  Enjoy your new fence. Thanks for asking here because now I know about these posts and will use them on my fence redo.