Adobe Esign Capabilities

Hi All,

I would like to know the following capabilities of Adobe Esign in terms API integration.

1. How do we customize the email functionality and only upload the document and create the widget URL. How can we achieve this?

2. How does we enable callback functionality with Adobe Esign. I would like to have the response structure as the same in not available as part of REST API ?

3. What kind of security is provided for request and response. Does it support oAuth2 authentication in both ways?

4. What is the vaulting option. Does it encrypt the document while storing in Adobe Esign. If we are not using this option of vaulting, how does Adobe Esign secure the document ?

5. How many days the document lies in the Adobe Esign storage when it is not a transient document ?

6. Does SOAP API is legacy and we need to use only REST API going forward?