I actually wiped my iPad and iPhone and went back to iOS 10. Which meant all my messages were gone. I then did a clean install and updated my iPhone and iPad to iOS 11. I noticed that when I went back to iOS 11, after a bit my messages I saved to iCloud showed back up again. Even though they didn’t show when I downgraded to iOS 10. What I cannot get to work is the part in iOS 11 where you are supposed to be able to delete your messages on one device. And they get wiped on all devices. I notice when I try, it gets deleted on one device. But the second device still shows that message that was supposed to be deleted. So I don’t know if that feature is enabled yet.