I have not worked with Elastic Search yet, however I have worked with the Search Framework. Assuming the principles are still the same (and from reading documentation, I believe they are), there are really only two options for search indexes - Full index and Update.
After a database refresh in any non-production environment, your indexes cannot be guaranteed correct until a full index has been performed.
I am not aware of any method of improving the efficiency of this, if that is what you are after.
Elastic Search will be integrated to PS Application. There is nothing as such to preserve in Elastic side or PS side. Searches in PS will be driven through Elastic server -
Were you able to figure a solution.
I am on the same issue and want to preserve Elastic Search Settings during a refresh