can you use a credit card at costco or only an atm card?

Debit card or Visa credit card.

Only if you use the Costco Citi bank CC. Ok therwise no.

Any VISA card

ATM/ bank / interact card and for credit cards Visa (USA) and MasterCard (Canada)

VISA or any debit card. They do not accept Mastercard.

Yes

Costco is no longer partnered with American Express, so i guess they are accepting card cards

You can use a credit card, debit (atm) card or cash/check at Costco.