There is three Kodi add-ons available to use with Plex. PKC integrates with Kodi Libraries so it has a “normal” Kodi appearance. Plex by Kodi has the traditionally Plex app look. Composite I’m not exactly sure how to describe but you can install all three and just see what you like as it is more a preference in what UI you want more than one working better than the other.
As for you non-working PKC you should be able to fix it easy enough. Please see the following thread for more information…