With the "Synchronize to a device" feature, there is a "Direct Connect" button you can press. If you enter the IP address for the other device, are you not able to establish a connection? Make sure you have one device set as the server, and you've tapped "Create Server" first, but then you should be able to connect if both devices are on the same network. If you have a router with multiple bands, make sure they are connected to the same band, and if it is a mesh router, you may want to disable the mesh features temporarily if they are causing connection problems.
As far as your question, MobileSheets can't stream data directly from Google Drive or Dropbox on all platforms. So all it would be doing is first downloading the file, and then performing the sync on a local file. You can just manually download the file yourself if that is your desire, or use the Settings->Backup and Restore->Restore Library from Backup feature to restore the backup file from the cloud (which also downloads the file first in most cases).
Regardless, I think you should be using the "Synchronize to a cloud folder" feature if you just want to synchronize the two devices. That's going to be much faster than having to create a full library backup file every time. Is there a reason you are not using this since you want to depend on the cloud anyways?
Mike
As far as your question, MobileSheets can't stream data directly from Google Drive or Dropbox on all platforms. So all it would be doing is first downloading the file, and then performing the sync on a local file. You can just manually download the file yourself if that is your desire, or use the Settings->Backup and Restore->Restore Library from Backup feature to restore the backup file from the cloud (which also downloads the file first in most cases).
Regardless, I think you should be using the "Synchronize to a cloud folder" feature if you just want to synchronize the two devices. That's going to be much faster than having to create a full library backup file every time. Is there a reason you are not using this since you want to depend on the cloud anyways?
Mike