IGN did a video/article and released some details about the game, this is just a copy and paste of some of those details and activities within the game that I found on reddit:
Can rob people
Dialogue choices
NPCs will react differently depending on your behavior, appearance, actions
You can pour coffee and check up on your gang
You can care for your gang and be rewarded for looking after them
Small scale robbery with Bill was shown
Demo took place in New Hanover (Handover?)
You can watch farmers herd animals, bugs in your ears
Demo was on base PS4
You can skin animals. It’s graphic, you can either drop the carcass or put it on your horse
Animals shot can be injured and attempt to escape. You can follow trails of blood to find the animal and then kill it.
Meat and animals will rot.
Amount of meat is based on how you kill it. Arrows will get you the most whereas weapons like shotguns won’t.
Your bond with your horse will result in different behaviors. If it’s strong, it’ll stick with you during gunfights
Your weapons will be stored on the horse. Take care of it. If it dies, you’ll have to start the bonding process over with a new horse
If injured, your horse can bleed out. If you wait too long, the horse can die.
The robbery takes place in Valentine. Not clear if it’s free roam, side mission, or story mission
Continuous camera, not different angles and shots. You can watch everything from one single camera angle.
Dead Eye returns. Camera angles change depending on how you kill the person using Dead Eye
You groom and feed your horse, calm it when agitated and it stays put when you dismount so you must be nearby to call it. You can grow a bond with your mount that makes it respond better to what you want it to do and makes it more relaxed
You can react to people in different ways I.e when meeting someone 'Greet or Antagonise'
Large carcasses rot if left out too long which equals less pay
You also get more reward for a clean kill (arrows) from butcher
Deadeye is basically the same as old game
Horses carry your weapons and they won't run off cliffs or do stupid things like before
You can affect the mood at camp by making sure they have enough food, resources which affects morale if positive they will be dancing, singing and telling stories
Found out names of some unknown gang members: Lenny, Karen, Sean McGuire (who is described as an Irish joker) Pearson (cook) Micha Bell and Sadie
Your hat can fall off and you have to go back and pick it up or buy a new one
New camps will be made often as the law heats up on Dutch
There is a huge level of choice in the game which will define who you are in the gang