When a recurring donation is processed through Soapbox using the Braintree payment gateway, Soapbox creates a new customer in the Braintree Vault as well as a Payment Method and Subscription for that customer. If an existing customer exists in the Vault for the donor that matches on first name, last name, and full address, a Payment Method and Subscription will be created and associated with that existing customer.
For one-time donations, event registration payments, and Shop order payments, a transaction is processed with no Customer record created in Braintree.