What does the QR code contain, and is anything sent to another service?

For euro accounts it is a standard SEPA payment code carrying the payee name, account, amount and your payment reference, which most European banking apps can scan to prefill a transfer. It is drawn on your own server as part of the page — no order or payment information leaves your store to create it, and no outside script is loaded. Accounts in other currencies show the details without a code.