If you can extract the subtitles into an external file, BatchDPG can handle them. Otherwise, you'll need to use something like AllToAVI first to create a *.avi file with your selected language and subtitles.
I have the same one in my other 3 switches. it's never had a problem with about 10GBs of space left. I'm going to check it when I get it so it may be Wednesday before I start downloading games on the oled.