The shop sales channel is available to merchants in regions where Shopify Payments is available. You can review the guidelines for the shop sales channel here. If you're using Stripe, then that would suggest that you're located in an unsupported region as Stripe and Shopify Payments can not be enabled at the same time. With that, Shop Pay (separate from the Shop sales channel) can only be enabled in your store if you are using Shopify Payments to process your credit card transactions.
With that, Google Pay is only available for store owners who are using Shopify Payments as Google Pay is not currently supported through alternative payment providers. More information on Google Pay can be found here.
Trevor | Community Moderator @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog