If Apple ever made it possible, it would be good if subtitles could be cast along with the video. During some recent travel we tried casting from infuse to hotel tvs. The subtitles did not come across unless mirroring. The penny dropped that external subtitles are probably added by infuse as an overlay on the video. Selecting the “cast” merely sent the base video stream.
Mirroring sometimes gave aspect ratio issues which could not be controlled satisfactorily, hence the request.
In the nice to have category.