A warning about Atlanta
Actually, I suspect there are several warnings about Atlanta given how big the place is. However, this is specific to international arrivals.
Atlanta has a landside terminal and then a series of subsidary terminals linked together by an underground train. International arrivals use the terminal furthest away from the landside terminal. You arrive, get off your plane, go through immigration, pick up your bags, go through customs. So far so normal.
However, to get anywhere else you then have to get on the underground. It doesn't matter if you're catching another plane or trying to get into Atlanta you take the train. Now, the train is the same train that passengers coming from landside to the planes use. So, they go through security before boarding the train AND SO DO YOU.
OK, so you bought some duty free booze or perfume in London, or on the plane. You have to do something with it because it exceeds the amount of liquid you're allowed to take through security. Either you drink/use it NOW or you put it into your bag or you sacrifice it to security. If you're going into Atlanta you put the bottle in your checked bag which you then put on a conveyor which takes it to the landside terminal so you can pick it up (again) there and the risk of the bottle smashing on that ride is limited. If you're going on another flight you put the bottle in your checked baggage, give it back to the airline and hope that their baggage handlers at Atlanta and Orlando don't give your bag a rough ride.
Me, I wouldn't buy anything en route......