If I remove a card from the Google Wallet app, does that stop any transactions on the card?
If you remove a card from your Google Wallet™ app you will no longer be able to use that card for Google Pay™ transactions. For the avoidance of doubt however, this does not prevent you from using your physical Westpac Mastercard®.
Note: if you have already authorised transactions via Google Pay, e.g. by checking in at a hotel or buying a subscription, these payments will not be processed once your card has been removed.