I have a pretty vast video library in PMS, but also a lot of TV Series and the kids movies that I converted from bluray discs to to ISOs. I would really like to keep them as is, so my intention is to use the Plex media as just another source a long with the folders containing my converted ISO stuff (since ISO is a no-go for Plex). This way I can mix all my media.
I have experimented with "Plex for Kodi" and "PleXBMC", but it seems that they only come up as Plex apps that I need to enter (and lose the connection to my ISO-stuff).
UPnP does really work either...