What's different from GTA 5: wanted level, guns, money and cars
Police need a witness, you carry four guns, cash can be lost, and cars need fuel. From Rockstar's previews.
Police only come if someone sees the crime, a victim reports it, or an alarm or camera catches you. There are six wanted stars, and police keep clues about your face, clothes, gun and car that you can get rid of.
You carry two hidden handguns and two long guns instead of a full arsenal. Auto-aim is off by default, and a slow-motion Focus mode works a bit like Dead Eye in Red Dead Redemption 2.
Cash on you can be lost, stolen goods go to fences, and almost any shop can be robbed. Cars need fuel, and stolen cars have to be registered or they vanish.
All of this comes from outlets that played Rockstar's previews in July, so small details could still change at launch.