Visio and PowerBI

Hi,
I have been playing with Visio and PowerBI.
I had created a Dataset in Excel and a Visio diagram, and mapped my fields to the shape.
I then published my Visio file to a standard FTP server - but the Visio Visual from the Visualisation marketplace does not accept a file from this location. By reading: https://techcommunity.microsoft.com/t5/visio/power-bi-visio-visual-anyone-managed-to-get-this-to-work/m-p/82427, it appears the file needs to be in a OneDrive for Business folder or Sharepoint For Business. 
Questions:
 1. Why doesn't box standard FTP work?  I am thinking from an angle of embedding a PowerBI report with a Visio visualisation plugin.
 2. What other limitations are there to using PowerBI and Visio together - is there a specific link to an article that may help me embed the understanding?
 3. We want to hook the report to a 'real-time' database - this will be highly volatile capturing data every second of the day 24/7.  Can you advise how we deal with the refresh interval - we don't wish to wait 15 mins, we want the chart to change in 'real-time' - please advise how I can do this?  Is this linked to the concept of a 'streaming dataset' by chance?
If someone can help with the above, I will greatly appreciate.
Thanks,
S