When you use a Chime Checking Account Debit card for purchases and you don't have any money in the Chime checking account then the transaction will just simply be declined so you won't be able to overdraft on the chime checking account using the chime debit card.
So you're safe if you accidentally use the chime debit card without money on it but you won't be able to make the purchase but you also won't overdraft on the chime checking account.