https://www.elastic.co/guide/en/elasticsearch/guide/current/_cross_fields_queries.html The advantage of being able to boost individual fields should be weighed against the cost of querying multiple fields instead of querying a single custom _all field. Use whichever of the two solutions that delivers the most bang for your buck.
https://www.elastic.co/guide/en/elasticsearch/guide/current/_exact_value_fields.html Avoid using not_analyzed fields in multi_match queries.