Mmm, but the point is that you can either select NAR and exclude it, or - as above - select ENG and use it exclusively. I'd probably go for the former, as badly-tagged streams would mean no audio at all on the latter, although many NAR streams appear as UND when I strip them out. Where you record them to doesn't matter, this would alter the file as it's recorded and that's it for good.
Of course, it also depends on your playback client - you only mention Plex server, but Kodi and VLC (as examples) allows you to switch between the audio streams on demand. I'm sure you can do the same if you're using something else.
