I don't know how it is or was on Linux but I replaced both Dropbox and OneDrive clients with rclone and my rclone bi-directional sync tool.
My tool is certainly slower than rclone directly since it has to list both remotes, do the processing, do the action, do the transfers, and then list them again. But I think my experience and takeaways may still be helpful.
In general, they are much slower that the always-on daemon. I think that is because the daemon listens for changes and only has to propagate those while my tool, and even vanilla rclone, will have to list the entire contents (twice in my case, once for regular rclone). But what I lose in speed, I make up for in robustness. First of all, OneDrive especially kept getting itself confused. And it has the performance hit of always running. This is as opposed to only running when I want.
I don't do it yet, but here is actually what I plan to do soon:
The files I need local access to, use my tool to keep in sync
Keep a running mount for everything else
It is kind of like selective sync but more manual.
Oh, and I don't have to worry about dropbox dropping support. As long as they have a public API and rclone supports them, I can too!
well, you did not write that so i wanted to be sure about that.
about rclone mount, you can pre-cache the folder/file structure, so navigating will be much quicker.
add --rc to the mount command
and run rclone rc vfs/refresh recursive=true
if you add a new file using the dropbox app or website, rclone will not notice it, be default, 5 minutes. https://rclone.org/commands/rclone_mount/#vfs-directory-cache
"changes made directly on the cloud storage by the web interface or a different copy of rclone will only be picked up once the directory cache expires if the backend configured does not support polling for changes. If the backend supports polling, changes will be picked up within the polling interval."
i do not know if rclone supports polling with dropbox, a debug log should show that.
for example, on a s3 backend S3 root: poll-interval is not supported by this remote