If the payment gateway stores customer information, this can be used to populate the contact information, billing and/or shipping address.
To specify that the payment gateway supports the express checkout flow, use the Aero\Payment\OffersExpressCheckout trait.
Since the express flow may not always be selected, the payment gateway must indicate if the customer is using the express checkout. This could be achieved by storing the status in their session:
public function isExpress(): bool
{
return session()->has('acme_using_express_checkout');
}