I have a QNAP TS-251+ NAS (connected via VPN + SMB if it matters) and would like to backup files from two machines to it (running Windows 8.1 and Windows 10), mostly user profile data (My Documents, etc.). I'm currently not using the snapshot function of the NAS, it's running a standard RAID setup.
I think it would be nice to copy the data on a file level to be sure they are accessible later. I have slight trust issues with proprietary backup formats and it would also give me access to the files from my phone. It would be a one-way sync, so that I can delete stuff from my PC, but it would still be available on the NAS until I delete it manually from there. I guess robocopy would be the standard choice here?
But I'd also like to keep file history. For instance in case files get corrupted locally and I don't notice before the server has been updated with the changes. I guess this would be difficult/impossible to do on a file level if one wants to keep the directory structure etc. So maybe a combination with a "file history" tool on the NAS?
Finally, I would also like to backup the whole NAS to some cloud storage in an encrypted way. Any good candidates for that?