I wonder if Starbucks is aware of the fact that there was quite literally a civil war over whether coffee should be on the blockchain, and that they're on the chain that doesn't want coffee.
As far as I understand it they will not really accepting bitcoin. They will use bitcoin (+ likely alts) so you can buy some StarbucksCoins. You can use those StarbucksCoins for coffee
The accounts at Bakkt will be custodial - Bakkt controls the keys. And charges fees for holding the account. And transactional fees. Like every bank does.
No, no coins. They, and users, will have to open an account at Bakkt. Users load some coins into it, and pay at Starbucks with Bakkt app. The $ amount is debited from user's account.