Jus wondering as a Mac user without mich experience: how is Safari in terms of privacy compared to say Firefox?

You’re using an apple product, you didn’t have any privacy in the first place. Browser choice isn’t going to change that either way.

Do you have proof of this? For example with the payment info on Apple Pay. It is all encrypted, not even the side I’m buying from sees my address or credit card info.

It’s the same with Google Wallet, too, so that doesn’t really demonstrate anything.