it's not easy to tell from afar, but my first idea and suggestion would be a slight variation of 2.
Create a jaw and give it a little nut-cracking. The dangling beard-strands, in an individual group, would be attached (stapled) to the jaw and then dangle. See this example: Character Animator Tips & Tricks (October 2016) - YouTube
Then, as a general thought, try using only two, or three strands of beard. You can use more than one dangle on each strand, it doesn't have to be one for each strand only. It's less weight on your graphic processor and also more realistic, possibly, for a beard, unless it's rasta, doesn't normally come in so many strands as top hair.
I've animated some bushes on a beach with that method to a nice effect. There was no time for individual grass strands, so that was a sort of "trick" solution, but in the end I found it to work perfectly. So that could look good:
Try painting the different strokes and giving them dangle weights here and there, instead of going for uber-realism and animating each single hair (I'm exaggerating, but you get the picture…).
P.S.: "… try using only two, or three strands of beard…" or only one, but with said method…
3. you could also make "two" beards.
a) One part, the chin-bone part, is part of your traditional lip-sync mouth - it's lower part, and it gets copied in every viseme.
b) A second part, the "hairy" part, is of the same colour, of course, but consists only of those dangling strands, be it one, two, or 15, doesn't matter.
That method would get rid of the nut-cracker jaw altogether and could also look good.
Stefan has some great ideas! Personally I would do a test run of 2-3 mouth shapes and see what looks best for your character, because I think so much depends on what style you're going for.
I do think copying a dangle beard for every mouth shape is going to get processor intensive and not get the result you're looking for. I believe dangles should carry through (I've added dangle to head turn hair before and it's looked okay) but it may feel jittery depending on how much the beard moves with each difference. Some kind of jaw solution is probably the safer bet, but it's worth experimenting with.
Thank you both for the thoughts. Another idea I came up with after reading your suggestions:
Not every viseme is radically different in height than every other. There are groups that are similar. My thought is to make 2 or 3 beards (seperate from the mouth shapes) and tag them as visemes (in addition to the actual mouths) with multiple tags per beard.
Ah yes, that could work nicely too. Good luck!