Hi Bret,
Fiori apps are based on odata services, and if you are talking about response time. I feel it should be quick update, as when you update any changes to backend, you get the response back from your backend saying "success" or "error". These messages would show up only when it checks backend and get back the response, whether it was updated or not.
If your remote location has good network connectivity, it should not be a problem.
Its just like working on sap system. As Fiori is nothing but your presentation layer for your gateway system.
You should have a good testing on these areas, as if the data is on large volumes. Network connection may time out. So services should handle this on first place.
Regards,
Tejas