Step 1: Create a selection field in contact module with two option as shown in the image. And set "Do not allow" for the customers you do not want to get paid online. This will apply a restriction and these type of customers will not be able to pay through portal or email link.

Step 2: Create a related field for the same in Sales order.

Step 3: Add the following automated action.

Hi,

You can use the Customer Wise Payment Provider In Website app to restrict certain customers from seeing or using specific payment providers.

Hope it helps