Q: Does adding a credit card to Apple Pay automatically add a card to the list of saved credit cards in Safari? Is there any relationship between these cards and the cards in Apple Pay? More importantly, if I delete a card in Safari, will it also be deleted from Apple Pay? I ask because I have a duplicate of one of my cards, and I don’t recall entering it. That’s the one card I’ve added to Apple Pay, so it seems possible there’s a relationship, and I really don’t want to delete the card from Apple Pay.
A: There isn’t really any actual “link” between the credit cards listed in the Safari Passwords & Autofill section and the cards used by Apple Pay.

That said, however, when you add a credit card to Apple Pay, iOS will also add it to your saved credit cards in Safari in an effort to be helpful and provide a consistent payment experience on your device.
The good news, however, is that this is where the relationship between the entries ends. Removing a card from the Passwords & Autofill section on your iPhone will not remove it from Apple Pay, nor will removing a card from Apple Pay remove that card from the Passwords & Autofill section.
In other words, the card information simply gets individually added to both places when you first set it up for Apple Pay, however there is no association between the two entries. This applies regardless of whether you remove the card from Autofill directly on your iPhone, or from another iCloud Keychain-connected device, such as an iPad or Mac.
.