Does schema normalization enhances query efficiency
It depends on the situation.

If normalization leads you to split your relations into multiple tables, and if you build those tables with primary keys and foreign keys which are defined to the database so that they are properly indexed, then in that sense query performance is enhanced.

Similarly, if your table is not in 1NF you might have to do expensive table scans and text parsing to find examples of a particular data item in a multivalued column.  In 3NF this column could be indexed making the query more efficient.

It's worth noting that normalizing your schema may also make your queries simpler and easier to maintain for the same reasons and in the same situations.

On the other hand, when data has become static (e.g. historical data) it is often denormalized to make retrieval faster.  This frequently takes the form of precalculating values, especially aggregate values.  This is the approach of data warehousing.  It is a good practice, as long as the risk of data insert/update/delete anomalies is very, very low or easy to manage.