Yes it is possible to still use Shop Pay with Airwallex if you meet the following requirements
1. Your online store is located in Australia, France or the United States
2. Your online store meets Shopify's requirements for that location
To activate you can follow the instructions here
If your store meets the requirements but you are unable to see the option to activate ShopPay please reach out to Shopify support with the following email template
Email Template:
Hi Shopify Support,
We have recently uninstalled the Shopify Payments gateway & installed the Airwallex gateway.
We are facing an issue where we don't see the option to accept Shop Pay wallet payments while using Airwallex for other card payments. Shopify support informed another Airwallex customer who faced this issue, that there is a delay between SHOP PAY becoming available immediately due to the way Shopify's eligibility criteria works. The Shopify support then worked with Shopify developers to apply an exception so Shop Pay express was almost immediately available when the Airwallex gateway was installed by that merchant.
I am therefore requesting for you to please review my account as well and get your team to apply the exception so that I can enable Shop Pay for my customers.
Thanks,
<Your Name>