Is Apple Wallet associated with an Apple ID or device?

For the passes, someone may have shared a pass with you and you then added it by accident, or you just unknowingly chose to add one. I'm unaware of passes syncing, but then again, I don't have two phones.

For credit cards though, I'll quote Apple's documentation:

After your card is approved, your bank, your bank’s authorised service provider or your card issuer creates a device-specific Device Account Number, encrypts it and sends [...] to Apple. The Device Account Number can’t be decrypted by Apple but is stored in the Secure Element — an industry-standard, certified chip designed to store your payment information safely — on your device. Unlike with usual credit or debit card numbers, the card issuer can prevent its use on a magnetic stripe card, over the phone or on websites. The Device Account Number in the Secure Element is isolated from iOS, watchOS and macOS, is never stored on Apple servers and is never backed up to iCloud.

So no, your card number is safe and has never been synced.