Hi,
Leaving out the queryEnabled(...) altogether will default to false. This configuration parameter is temporary and has been put in place for testing with N1QL DP4, where the engine is separate.
The client will work with Couchbase Server 4.0 (currently not even in dp nor beta), where the engine is built-in and can be present in a subset of the nodes, by discovering automatically if the service is available and on which nodes.