What are the impacts of having and not having an opensearch-custom-codecs plugin?
There is no impact of having or not having an opensearch-custom-codecs plugin if it is not used. Functionally wise, there are new codecs provided.
does it have dependency on any other opensearch plugins?
nope
having opensearch plugin code can increase the enhance query performance, reduce storage, custom serialization.
Not having opensearch plugin has default JSON, potential performance.