The Snap just performs the wielder’s will which is made quite clear over the events of Avengers: Infinity War and Avengers: Endgame. It’s made the most clear when Tony asks Smart Hulk what to do with his Snap.
Tony: You remember... everyone Thanos snapped away five years ago and just bringing them back to now, today. Don't change anything from the last five years.
Later on when Smart Hulk has done his Snap he again makes it clear that he had control over what the Snap did because he tried to bring Nat back.
Smart Hulk: You know, I tried. When I had the gauntlet, the stones, I really tried to bring her back.
Just to be complete Thanos’ Snap was only to kill half of all life and so that is why it didn’t affect ships or the like.
Gamora: The entire time I knew Thanos, he only ever had one goal: To bring balance to the Universe by wiping out half of all life. He used to kill people planet by planet, massacre by massacre...
Thanos: Little one, it's a simple calculus. This universe is finite, its resources finite. If life is left unchecked, life will cease to exist. It needs correction.
Avengers: Infinity War
The implication is then that Tony’s Snap was to destroy Thanos, his forces and equipment so that they could win the battle. A deleted scene shows Gamora is still alive and she was originally on Thanos’ side and so the Snap must have only been for those loyal to Thanos at the time of the Snap.
And of course the Snap can affect none living things as we see in all of the Snaps. In Thanos' first one it destroys clothes and "personal items" of those who are Snapped. In his second one he destroys the Infinity Stones.
Natasha Romanoff: Where are the stones?
Thanos: Gone. Reduced to atoms.
Bruce Banner: You used them two days ago!
Thanos: I used the stones to destroy the stones. It nearly killed me. But the work is done. It always will be. I am... inevitable.
Then in Smart Hulk's Snap he just reverts Thanos' Snap which brings back the clothing, personal items etc. Lastly, Tony's Snap affects clothing, ships and the like.