Is this possible? Is there a way to make it so that when a user makes an account with my shopify store they can then select and purchase a (monthly) subscription plan that I have set up in Braintree.
The idea is to have it so the user's shopify account information is used to setup their subscription package that I have set up in my Braintree merchant account.
Yes. That is totally possible. I have done exactly that with Stripe, and clearly Chargify also works that way. You can setup a Webhook to send yourself new accounts from Shopify, and then code up the setup in Braintree.