Hi Charlie,
Apologies for the late reply, I was out of the office on vacation last week.
> Is there any more information on if we will be able to use the Dashboards on a mobile device?
Dashboard apps are only accessible in web browsers on desktops and tablets. We don't currently support viewing them on smart phones because of the very small form factor.
> ... I don't see the option of single / multi-display.
This is by design. Dashboard apps only support a single display. However, you can stack elements on top of one another if you want to include more of them in the app.
Dashboard layout—Operations Dashboard for ArcGIS | ArcGIS
Hope this helps,