Subler -> BY FAR the best one. But it's difficult to get used to.
Subler is by far the best. I use remux to remux an MKV's DTS track to an AC3 6-channel "Surround" track, since Subler has some issues when doing DTS conversions. But with Subler and remux, one can take an MKV with a DTS track to an M4V with 1) a stereo track, 2) a surround 6-channel remux of the original DTS track, 3) the passthru'd DTS track, and 4) Subtitle/chapter tracks if they were present in the MKV (subtitle tracks can also be found online in random places. Check the track lengths/release origin to make sure the srt subtitle track you find coninsides with the release you are converting.
Handbrake is nice if you are doing the Blu-ray ripping yourself, after you have used MakeMKV to get the parent MKV for Handbrake to use. But for just remuxing, Handbrake is a horrible waste of time and CPU. But it IS a tad bit more brainless to use, so a lot of people just use that to remux too.
Again, Subler doesn't have the best instructions, but if you have any questions someone smarter than you has done it before on here or on the Subler Google discussion page.