It should be released before December, likely in November, but no guarantees.
Sync should work by itself in the background. You can have a few remote vaults, and if you sync to the same remote vault on two devices, your vault will stay synced.
Features include end to end encryption and version history. Not sure what you mean by “limitations”, would appreciate it if you could be a bit more specific. Price could be one limitation, since if you’re up for it you can use third party sync + encryption service to achieve pretty much the same thing.