To be clearer on a part that I accidentally glanced over, I’ll use Yatse (connected to Kodi) to play the stream on VLC Android, which then can proxy cast to the Chromecast, no plugin needed. But the Yatse part is just a convenience - as long as you can get the video stream directly (ex. http://192.168.x.x:8080/vfs/%2Fmedia%2Fuser%2Fmovie_drive%2Fmovies%2Fgood_movie.mp4 or similar), VLC android can play (and cast) that directly. One possible way to get this URL is to access the Kodi web interface, stream a video to your browser, and copy the streaming link while it is playing.
And as for subtitles, I think they cast fine too as long as they are part of the video file itself and not a separate .srt.
I have been toying with Feishin as a client player with some positive results. It operates as either desktop or web…