Report Server Excel Add on & Tranmission Type

I have the below questions if somebody could help?

Question 1: We are in the process of moving from Power BI Service to Power BI Report Server to keep data on premises. Is there a Power BI Publisher for Excel version configured for Report Server. What type of connection does it use to access the content published to the server?

Question 2: Our installation of Report Server is planned using an off-site central data centre on company infrastructure. Why type of transmission occurs when data is published from Power BI Desktop – Report Server Edition to the Report Server itself?

Thanks

Aidan