You still have to double tap the side button from the wallet app to prompt for Face ID and then arm Apple Pay to communicate with a payment terminal. I think Apple seems it a security measure to verify Face ID before proceeding with payment. It’ll arm your default card I think. If you select a specific card while in the wallet app (when you can see the latest transactions for that card) and then double tap, it’ll arm that specific card instead. More on reddit.com

If tap to pay is accepted, it’s highly likely they’ll accept your Google Pay. Most places have a little sticker for Apple Pay, Google Pay, and then Visa, MasterCard, etc. It works the same as with a physical credit card! Just hold your phone over/tap it onto the card machine. I like to open up the wallet on my phone first before tapping, but I think the devices are actually smart enough that you don’t need to do that. You will possibly need to put in your passcode/authenticate yourself before the payment goes through, so just be ready for that. More on reddit.com

Tap to Pay is a business tool, not a peer to peer tool. You can use Square without using any unwanted features. They charge the same either way. More on reddit.com

If your bank is not listed here, you would not have a way to make payments with your phone via NFC. https://support.apple.com/en-us/HT204916 More on reddit.com