connections across multiple gateways

Hi all

I have a couple questions regarding gateway connections and gateways servers.  I appreciate any insight.

Here are my gateway connection questions:

1. I have a reprort with connections to Excel files hosted in Sharepoint online. When I publish to the service, it seems they must be included in the gateway server. Is this correct? I was under the assumption that I did not need a gateway to connect to this type of source as it is not really on premise. Or is it requiring a connection for these files because one of the connections is to an on-premise database (and therefore requiring across all connections)?
2. In a report that has multiple connections to sources, do all the sources need to exist in the same gateway? I was trying to split them (for logisitical management), but it seems I cannot apply my settings in the service if they do not all exist within the same gateway.

My gateway server questions:

I am looking for the best way to set up gateway servers for my organization. Originally, I was thinking of setting up a gateway server for each region, but depending on how my question (2) above is answered, that may not work well. I am looking for a way to manage connections that will grow extensively as we use Power BI to support clients. I guess what I am asking is, how best can I manage gateway servers and connections when the use is growing exponentially? We do not want things to grow out of control and want to be able to relatively easily edit/manage connections as needed.

Thanks in adance for any suggestions and support.