Can Google Pay or PayPal be my payment method instead of Apple Pay?

If PayPal is supported as a payment method in your country. Please review the support article below for information on what is supported in each country.

Payment methods that you can use with your Apple ID - Apple Support

I believe so. I have tried to set a Wallet Payment method with a PayPal for a short event business period. It was intended to be a temporary method. It was successful in that and was able to be removed and replaced with my previous primary.