l suffered major issues when migrating from a C8 to a C8 Pro with a few LR devices. This migration was right after the LR support was added. It was a mess and probably could of been handled better with what I know now. I suffered from a few bugs that compounded to make it a complete mess at the time. In the end though I ended up having to redo everything on my zwave radio. If i remember right there was also a need to migrate my hub with the cloud backup for migration, and then perform a second restore taken from my old hub without radio data.
I don't have the cloud backup service, but i do think it is backed up there. I can't speak to the Smartstart data.
No ghosts now as like I said I ended up reloading everything zwave related.
That was the sweet spot i found for including as fast as possible. I found that generally speaking with 4 enabled at a time, i couldn't cycle through them fast enough to actually have more then 4 going at a time. It worked reliably and was consistent in my case.