Does the Smart Switch app move WhatsApp data across correctly, e.g including conversation history - or do you still need to do the manual backup of the db crypt files?
From my experience it didn't even "move" the app itself, I had to reinstall this manually from the store. So you will have do manual backup and restore.
The Smart Switch app is bit crap to be honest. It hardly moves any apps with the data as well and I had only one app which had existing data. Everything else I had to do again or re-sign in again.