What kind of bank card can I use when traveling to Taiwan?

I personally recommend using UnionPay card, as the rates are more cost-effective. It saves money than using RMB cash.

The following is for reference

1- UnionPay cards can now withdraw Taiwan dollars directly from ATMs in Taiwan (deducting the RMB in your account). In addition to street food and night markets that require cash, department stores UnionPay cards are accepted for payment in hypermarkets and hotels.

2-International credit cards can be used for purchases in Taiwan.

3- Bring some RMB as appropriate, as many attractions can be spent in RMB.