The Option/Media Network/Add or Configure DLNA Servers... under Advanced has a checkbox (See Capture 5)
I have a Samsung TV that is visible to MC as a DLNA device, but is also connected via HDMI to my HTPC, so I don't have exactly your setup. Therefore, my system may operate differently.
I ensured that I had a TV Show with Subtitles at the beginning, and turned on, to test.
I then ticked both the "Present Captions Resources" and "Present Subtitles Resources" that you have in your image Capture5.
I then clicked on my Samsung TV zone under Playing Now, to make the Samsung the default playing zone, and then double clicked the TV show in Standard View to get the show to play on the Samsung, via DLNA. The TV switched to its DLNA input and started playing the show with Subtitles visible.
Up to here, all I have been doing is setting up the way you have, even though I don't have a separate screen for MC.
While the show was playing I pressed the Return/OK/Enter button on the Samsung TV's remote, which then shows the Pause, Rewind, etc. buttons on screen. The last button on that screen is the Settings button.
Selecting the Settings button pops up a menu, the top item of which is the Subtitle item.
Selecting the Subtitle item using the Samsung remote showed that Subtitles were turned on. I turned them off. Exiting the menu, the Subtitles were no longer displayed on screen.
Note that I tried to turn the Subtitles back on using the above menu, but despite the setting changing to "On", the Subtitles didn't return. I suspect that the Subtitles item needs to be turned on when playback is started. Stopping the show and restarting it using my HTPC remote restarted the Subtitles, but also restarted the show from the beginning.
Note also that the Subtitles button on my Samsung remote, then one that would normally turn on Teletext and Subtitles for OTA broadcasts, did not have any effect when doing this testing.
So basically, use the MC DLNA settings to turn on Subtitles for the DLNA server in MC. Then use the Samsung DLNA Client functions to turn off the Subtitles if you don't want them for a particular program. BTW, I am assuming that you want Subtitles normally turned on for these shows, or you could just turn them off for the particular file from inside MC. If Subtitles are off for a file in MC, they won't show up on the DLNA Client, at least in my environment.
As for the definition of all the Subtitle Jargon, Google is your friend.
P.S. Didn't know how to embed the images so they are all attachments... ?
It is better to attach the files as you have, rather than embed them most of the time. That way users who view the forum only download a thumbnail of the file unless the deliberately click on the thumbnail to view the larger image. That speeds up viewing of the forum, and reduces the download size for users.