Australian Subtitles in converted mp4 files?


just a quick question before I buy a lifetime access license.
I’d like to convert existing wtv files into mp4 files to play in play in Plex. Will it be possible to store the closed caption information in the mp4 file and then to turn it on/off when playing the file (ie not burning in the captions)?
The wtv files are recorded Australian TV shows (not entirely sure how the subtitles are stored here in free to air TV).

Thank you for your help.