I recently wrote an article about
Offline file conflicts with SharePoint Online
that ran through the process of what happens when users go offline when working on shared files.
After doing some more poking around in the latest OneDrive for Business sync client I found this under the Office tab in Settings:
You can find more information on the first option here:
Use Office 2016 to sync Office files that I open
If you turn off this setting, Office will no longer be able to automatically merge changes from different versions of documents. You’ll also be prompted to upload a new copy of a file before you can share it directly from an Office desktop app.
You can also elect how to handle Sync conflicts, which by default is set to Let me choose to merge changes or keep both copies.
The defaults options are going to suit most people but you can go in a customise these if you wish to improve how conflicts are handled in your environment.