Personally i open 743 from the cutoff but i had a debate about this with a friend of mine. I tried to convinced him to open, he tried to convince me to fold :) None of those were succesfull, i still think we can open this. But it should also depend on your opponents, if you feel uncertain in some spots, and players behind you are very good than you don't lose too much EV by folding.

But if some of them are too tight or you feel that you play better postdraw then i think it will be a mistake to fold.

HU 2-7 triple draw is really a different game. I think my full ring (4max+) is a little bit stronger, but i played still a decent amount of HU.
It also depends on your opponent, but i think i open something like
75+ and 83+
and other hands with some blockers (so 866, 766, 844, etc.)

Still struggle to figure out the exact defending range, so can't give you an exact answer. It also depends heavily of my opponent, game flow how i play. However it should be a little bit tighter that we open.

This is a really tricky spot what to with 8765...
I think drawing to 865 is the third best option here. You said that we can catch a 2,3 and have a strong draw. However if we kept the 8765, now we have a made 8765-3 or 8765-2.
In these blind on blind battles we are certainly doing better with marginal pat hands. Also if we make 8765-T we should pat that (and try to overrepresent), but it also depends how the hand was played and when we caught that.

It would be completely different if let's say EP opens and BTN calls. Then even with 8765x we have an easy fold from the BTN. (we might can consider call/take 1, but it just turns our hand faceup, and also we have very bad playability). Deuces should be dead, so even 765; 764; 865 should be folded there multiway (because multiple deuces are very likely out).

I still think that here, BB vs SB the best way is to play as a 8765 1 card draw IP.
Then 765, and third 865.

There might be a small problem, that with 8765 we might oversnow. I have a general rule to only snow if i saw 2 extra good cards to prevent oversnowing. (so let's say i start 8765-7, i discard the 7, and then i catch a 4...now we can snow). With 8765 it's really tempting to snow even with only a 1pair blocker.

I dont think that there is too much difference here what blockrs to use for snow. I think 8765-5 and 8765-8 are close to the same. However in general lower pairs/blockers are better (and trip blockers are better than 2pair, so 8765-66 is a much better snowing candidate then 8765-65).

Unfortunately there are no simulations yet for those games, so i just use my own judgement. I try to discuss these new/unique situations with friends and try to get some conclusion by doing that.

I also plan to make a live mix game review, where i focus mostly on these new games (dramaha, badeucey, badacay). I played some live hands just before covid got into our life, and will review those in a powerpoint format.

Hope that will help you and we can discuss those games there.