Just adding to this accurate statement, you can also sync a vault in iCloud. So there are at least three syncing methods:

1. 1Password Cloud

2. iCloud

3. Dropbox

And at least 2 and 3 can be used simultaneously, which is what I do, with my main vault in iCloud, and temporary vaults, e.g., passwords for a particular job, in Dropbox.

There’s also still the WiFi sync method which you can use to sync between devices without that information ever leaving your local network.