...
In cases such as this one, where the Braintree is in use in the campaign, it is still working as before.
...
Please that if the user removed the Braintree from the Payment Providers in the Campaign Settings page but didn't save the changes, he/she is still able to include it again within the payment providers.
On the other hand, if Braintree is removed from the Payment providers section, of the Campaign Settings page, and the user saves the changes, then he/she is unable to add it again in the payment providers.
...