Any time you change the settings of the PhotoVia Publish Service (or any Publish Service), Lightroom will ask you if you would like to republish these photos. Most of the time, you should select "Leave as is," since there is no need for you to republish. If you did select "Republish All," the photos will be marked for republish, and during their publishing, they will replace their existing photo counterparts on Google Drive. There will be no duplicates in Drive or the PhotoVia App.
However, if you re-authenticate PhotoVia in the plugin settings with a different Google account, you may indeed want to republish everything to this new Google account. This would be a specific instance where marking photos for re-publish does make sense, but most of the time you will simply select to "Leave as is."