You get the full customized code of each email template in your design. To use the email code, you simple copy/paste it into your Shopify Admin replacing the old email design.
This means that you will have full access to the email template code itself, can make tweaks, and do what you like with it. You can also come back to the app at anytime to make adjustments and updates.
Our only restriction is that you only use the template for the store that you purchased it for ;)