Hi. I recently came your route and after some months of practice I am averaging 21-24. Your question has no simple answer, it all depends on your preferences, turning style... but I have bought a lot of those cubes this year so, I can tell you this:
Dayan Zhanchi: the stickered version is quite good but surpassed by Moyu and YJ new cubes. the stickerless version has a very different feeling and I would not recommend it, it is far too uncontrollable for your/my speed. Also, both of them pop once in a while, but all the others below don't (unless I explicitly say otherwise).
Fangshi: it is not bad but it is not as good as other options. It feels very light in the hand (if you like that) but tends to catch a bit. Good thing: it is quite silent.
AoLong: I got a V1 and I get A LOT of corner twists (I like somewhat loose tensions, but even after tensioning it a bit more, still corner-twists like crazy). It is fast and controllable and has amazing corner-cutting, so it doesn't force you to be accurate while turning, which can be good or bad, depending

I don't like it's bubbly feeling and rounded edges so, after a while I changed it for another one (see below). If you still like it, everybody recommends to get a V2.
Weilong II: great cube but a bit fast for me, I have it in a drawer for the time when I get to sub-20 territory and have much more accurate turning. Then I think it will be my main. It does not corner-twist at all and has a much more "squarey" feeling so I prefer it to the Aolong (just a matter of personal taste).
ShengShou Aurora: very good cube, good overall feeling, quite fast, almost no corner-twists (but some) but I make mistakes at times because it tends to slide and turn in unintended ways / axes if not accurate. Also very sensitive to good tensioning and lubing. Don't tension it too tight or you will lose a lot of corner-cutting and without proper lube it does not corner-cut at all but well lubed it can be a very nice cube ...still not quite the best.
The others you have mentioned I cannot tell but I have tried others you don't mention:
Moyu HuangYing: Surprisingly good. Very noisy and with clicky-clacky feeling but it stays perfectly square during solves, which I love. It is really fast and forces accurate turning. It was my main for some time. Problem: it's got open corners and I sometimes hurt a nail by getting my finger accidentally inside the cube.
YJ Sulong: Also good and dirt cheap, more silent than most cubes (not as much as the FhangShi) but a bit "sticky" and slow unless very well lubed and even then not as fast as others. Not a bad cube at all but not the best either in my opinion.
YJ Chilong: Improvement over the Sulong. Fast (but not as much as Weilong), squarey and a perfect mix between the Sulong and the Huangying. Result: A great cube for intermediate cubers and my current main. I have done like 5000 solves with it and it's still great. With a bit of lube it is just fantastic but be careful not to lube it too much or it will be difficult to control. Bad thing: stickers are bad, I will have to change them soon, I have hurt my finger twice by having the border of a sticker under my nail 'cos the stickers are too hard and tend to peel and chip. But this should not keep you from trying it.
There are others, like the HuangYing v2 (LiYing, I think it's called) that people say is better than the HuangYing, so it must be great as well but I have not tried it... yet
Regarding availability on SCS I cannot tell. You'll have to check by yourself ;-)
Hope this helps!