For payment in store, it is standard EMV contacless payment (with some specificities for HCE) like for contactless physical credit card. Therefore you should be

For payment in store, it is standard EMV contacless payment (with some specificities for HCE) like for contactless physical credit card. Therefore you should be able to pay with any NFC enabled Point Of Sale connected to payment networks (Visa/Mastercard at least I assume for Android Pay). This payment solution relies on tokenization. Tokens are mapped to physical payment cards (Google will probably act as a Token Service Provider). Tokens once provisioned on the mobile hold among other things a Digitized Personal Account Number + a set of single use payment keys (or limited use keys) for payment.