For each of the “Lockal Couchbase server with application”, are each of those separate clusters?
Assuming they are, you can use XDCR to sync data between them. You can set up an XDCR from each Lockal to the Central cluster and/or to each of the other Lockals as well.
As far as queries go, you would likely NOT send a query to every cluster. The application would query the Lockal cluster, and avoid going across VPN tunnels to Central.
With XDCR, you will probably need to think carefully about how you are going to resolve data conflicts (if applicable) and/or doing advanced filtering.