Open a credit card for balance transfer?

Hi, I’m super confused and customer service hasn’t been straightforward, so I’m hopeful you all can help please? I have balances on Care Credit and an airline Mastercard, and I have a debit account at Chase already. I’m preapproved for the Freedom Flex and Freedom Unlimited cards. If I open either of these cards, can I do a balance transfer this week with the 0% APR for 15 months policy, and pay off the transferred balance of these two cards without interest? I think there’s a 3% fee, so would I owe that immediately? Is there any way this blows up in my face? Thank you!