You can use your Salesforce org to create the quote or proposal and Conga Platform to initiate the billing by using the QTC profile setting.
When you set the QTC Profile on the order header to Conga Platform, the initiate billing logic on Salesforce is bypassed, and the billing is initiated in the Conga Platform. After the billing is initiated in the Conga Platform, you are taken back to your Salesforce org, where you can see the billing schedules.