I know OneDrive will not run the C-drive out of space and will prompt the user to reduce which folders are being synced. Is there documentation on when it will stop? Does it stop at 2% free space, or 100 MB, etc.? Working to get to Files on-demand, but not there yet. Customer concerned if we migrate file share to cloud, and then it syncs to desktop, when is threshold hit and doesn't want to jeopardize desktop availability and/or responsiveness.
I found an updated article that specifies the answer.
If syncing the user's entire OneDrive would cause the available space to drop below 1 GB or if the size exceeds the threshold you set (on devices that don't have Files On-Demand enabled), OneDrive will prompt the user to choose folders to sync. For info about setting this threshold using Group Policy.