My experience with customs (Global Entry) and clearing TSA:
—DTW I’m usually always thru customs and clearing TSA to re-enter the A concourse for a connecting flight (I don’t live in DTW even though it is in my user name) in no more than 15 minutes. I’ve never had long waits, sometimes no wait at all.
—ATL can be a crowded mess, mostly waiting to clear TSA for a connecting flight. No issues with customs. The TSA I>D experience at ATL has never been quick for me.