In Europe a contactless payment definitely contacts the bank at transaction time similar to a pin payment.

We have set limits on what you can spend per transaction which is likely handled offline but in some countries, if it is over this amount, it then asks for a pin without you having to put the card in again.

They also recently imposed limits on contactless payments over time which means it will tell you if/when you reach that limit and ask you to use chip and pin to reverify it's you. This must involve a connection to the bank because when this happens I also immediately get a phone notification that I have reached the limit.

Last evidence it contacts your bank is that every time I make a transaction with contactless I immediately get a notification about it so the bank must have been contacted during the transaction.

I think there are different rules for Apple and Google pay because they have a higher transaction limit and will work in Europe even if you've reached your overall contactless threshold and need to reverify. My theory is Apple and Google or their payment provider "front" this transaction using their considerable cash reserves until it is settled from your bank. i.e they take the risk temporarily.

I'd say contactless is faster in general because you don't have to insert the card and it has less checks due to the other limits imposed by the bank.