I'm kind of in the same boat as you. I'm using LR for file management, metadata, etc., and planning to switch over to CO for processing.
So far, what I've found is that CO stores its settings in sidecar files distinct from the .xmp files. They end with extensions like .cot, .cos, and .cop. As far as I can tell, CO doesn't alter .xmp files unless you make metadata changes from within CO.
If you need to make sure CO can see metadata changes made in LR, you'll want to either Ctrl/Cmd-S to save LR's metadata updates to .xmp on a per-file basis, or turn on the option to automatically write XMP changes in LR (though there is a performance hit for this path).
Good luck to both of us.