Merchant profile override
This enables you to override the global merchant profile (Worldpay Merchant code) based on payment method. If the override is not set, Magento uses the global merchant profile for all transactions.
To configure these settings, go to Stores/Configuration/Sales/Worldpay/Merchant Profile Override Configuration. See screenshot below.
This enables you to use a different merchant code to process PayPal and AliPay orders.