Hi,
odrive will make a best effort to determine if the files are the same. Here are the steps you should take to merge the local content of the other apps into odrive. We will use Dropbox as an example, but the rest should follow the same pattern.
Close the Dropbox app so that it is no longer running * very important *. If you move data out while the Dropbox app is still running the Dropbox app could pick up those changes as deletes and delete all of your remote storage
Unsync everything but the top-level odrive/Dropbox folder. The easiest way to do this is to right-click->unsync on the odrive/Dropbox folder, wait for it to be replaced with Dropbox.cloudf, then double-click on Dropbox.cloudf to only expand that top-level folder.
Move your Dropbox data from your Dropbox folder into odrive/Dropbox. Make sure that the folders are “lined-up” so the cloud and cloudf files will be replaced with the local versions. I strongly recommend performing the operation with only one folder, first, to make sure the results are what you expect.