If the source DVD includes captioning options this player makes them available to you - controlled via menu via the remote. You cannot alter the size or placement of the captions. The size of the captions works fine for me.
To be honest I think this is made for TV's only but I'm not an expert at all, the employees at Best Buy are very knowledgeable or the Geek Squad can answer your question.
You must connect this to some kind of stereo receiver for it to work. It cannot be used alone. You need the stereo receiver to transmit the sound to a speaker system.