Which is the best way to update a structure from PROD to a DEV/test environment? The structure exists in DEV/Test environment but is not the latest as teh database has not been cloned from prod for sometime.
Is plmxml the best way? If so which transfer mode to be used? If there is any other way, please suggest.
I would suggest to delete the structure in your DEV Environment completely. Then do a plmxml import.
Which tranfermode to be used really depends on the structure contents and what you need from PROD to DEV.
ConfiguredDataExportDefault transfer mode would be sufficient for most use cases or scenarios.