The Conga Templates UI allows your users to create robust and dynamic templates using Conga's easy-to-use user interface. Composer supports templates using Powerpoint, Excel, Word, PDF or HTML Email formats. 
If you are integrating with Salesforce, you can use the Composer Template Builder to create Composer templates in addition to using our JSON integration. For more information on using the Composer Template Builder, see our section on The Template Builder. You can also use Conga Queries to gather data for your templates. For more information, refer to Creating Conga Queries

For all other merge data, you will need to apply your own merge data via a single JSON Payload.