1. About bank cards. I think the "bank card" you mentioned should be exactly the "savings card" or "debit card" we use every day. Because in a broad sense, credit cards (debit cards), savings cards (debit cards) and checking cards all belong to bank cards.

2. About the combination of savings card and credit card. This usage is a combination of the mainstream. The reason why it is mainstream is because it is common and convenient. At present, almost every unit pays wages with the company's unified savings card (such as China Construction Bank Longka), and every household or person has a savings card, which is the main reason why the combination of savings card and credit card has become mainstream. Moreover, when handling credit cards, you need to provide a savings account for regular repayment of credit cards, and most people regard the savings card account as the first choice for repayment accounts, which is convenient and fast.

3. Single credit card. I've never heard of a credit card without a savings card. Of course, in big cities, you don't need a savings card. Just swipe your credit card, but there should be.

4. Conclusion: I suggest you choose a combination of savings card and credit card.

I hope my answer is helpful to you!