Which version of Couchbase Lite are you using ? You can filter by documentIds or set up push filters on replicator which determines what gets pushed up to server. It looks like you have already posted this question here which was responded to
Push mode of continuous does not impact what gets synced. It determines if replication happens continuously (i.e. any time changes happen on either end subject to network connectivity ) or if it is one shot (syncs the changes and closes the replicator)
The direction of replication is determined using config.replicatorType (Push or Pull or PushAndPull)
You don’t have to do that. Unless you want the data synced up (pushed) from the clients to be stored in a bucket different from the rest of the server side documents.