In Google Pay there are 'profiles', i.e. countries. For instance, I have an US profile, where it is possible to add PayPal as a payment method, along with MasterCard and VISA (credit & debit, not pre-paid), checking accounts and Google Play balance.
If I switch in pay.google.com => Netherlands the only options are MasterCard / VISA credit & debit cards; nothing else.
Furthermore, I got Google Pay working with my Netherlands profile, the US profile was rejected because 'Google Pay is not supported in the country you're in (The Netherlands) (?!). However, this was not with my bunq because I'm not a Premium user and Google Pay doesn't accept Maestro cards, so I used another (UK-β¬) bank.
The Google Pay App was sideloaded, what clearly a security risk is, especially if used with as payment/bank App!
In my experience, there is nothing faster than NFC paying with Google Pay (I've used several others). You have to unlock though (finger). It works several times offline too (with encrypted tokens). When you get online, used tokens are supplemented again. It doesn't send your card numbers anyway but uses tokens instead.
Anyway, I hope this info makes it a bit clearer how things work or don't work.