"Evidence synthesis refers to any method of identifying, selecting, and combining results from multiple studies. " A literature (narrative) review is one of the most common types of evidence synthesis.
"This document is based on the PRISMA Statement (evidence-based minimum set of items for reporting
in systematic reviews and meta-analyses) extensions for systematic review protocols and scoping reviews, and materials developed by The Campbell Collaboration" If you decide to do a systematic review instead of structured or narrative, this document is a good place to start.
"This toolkit contains resources, templates and other useful materials for researchers undertaking evidence synthesis projects such as systematic or scoping reviews." The templates are for task lists, Covidence screening software, and mining seed papers for search terms.