HenkdeB From what I've found, a third party sync may be your only solution. It's possible to tell OneDrive to keep files stored locally, but that can be inconsistent, and it still works only on your system drive. It's also possible to tell OneDrive to keep cached files on a different drive, but that is even more inconsistent, and the actual files still don't live in the OneDrive folder--just pointers to the files.
GoodSync isn't a service I've tried--I'll have to give it a look. All the other third party sync clients I've looked at or tried want to pull files from the cloud only when accessed, and they generally store the file cache somewhere other than where the files appear to live. This is largely where the industry is moving, accelerated by Apples Apple File Provider framework that they are forcing sync clients to use. Until there is enough pressure from people like photographers, who need to keep local copies of their synced files, I don't see that changing. It's an issue for lots of folks, but the cloud providers really want their users locked into their services.
Ken Tryon