Adding hard and soft subtitles to a video
You can do this via ffmpeg.exe.

For a guide to installing ffmpeg check the first part of this video here: 
                
            

For hardsubbing you can check this video here:

                
            

Assuming the above is now known:
In your specific case you are going to want to make copies of the video stream and then hardsub the copies with the subfile desired.
To learn about mapping streams you can read here:
https://trac.ffmpeg.org/wiki/Map  

All the information is above in those 3 links to get you going with ffmpeg for the purposes needed. If you need help formatting the command for your specific situation please provide a thumbnail of the streams in ur video you want to modify and I can help you with the specifics. Pay close attention to the specific tidbits mentioned in the content above, as there are many traps you can fall into along the way. I'll help you with those though if needed.