I really dislike Gearbest, and it may be more trouble then it is worth, but they had the Hotcig VS not to long ago.
As for the three you mention, I'm going against common opinion, but the FEV 3 just never did it for me, flavor is just a bit on the weak side, not bad, but not as good as many others. I've found no matter the build or placement of coil it ends up being slightly muted.
Horizon is better on the flavor department, and can be had with a nano set up which is a plus for me, also offers some pretty decent air flow options with a decently large range, unfortunately the range is accomplished with grub screws blocking off 1 or more of the 4 ports with grub screws, extremely tight air flow being accomplished with 3 blocked, fourth with a center drilled grub. little fiddly but works well enough.
couple things I don't care for with the Horizon, both fixable, but annoying enough to make worth mention. The juice feeder holes are a bit on the small side for High VG liquids, it will work but tends to starve just enough to be noticeable unless you get wicking just right. Easy fix would be to run a drill through them, which I never did get around to.
The second issue, the top of the chamber is a plate, and held in place with an o-ring, when it gets juicy it spins easily, which end up messing up your build. Polishing/reducing the chimney just a tiny bit, or a little tighter o-ring should fix it, just never got around to it. Kayfun type deck is a really easy build, 22mm is another + to me as well.
Finally the Kronos, my favorite of the three, Nano option, fairly short overall height, especially with nano tank, easy wicking/build best flavor of the three. Top fill capable (not the best design but works) Drop deck for easy access to build. Decent airflow with good range of adjustment. 23mm could be a negative depending on preference, doesn't bother me.
Woo, a little long winded, sorry for that..
Kronos nano tank
Taifun GS, Horizon nano tank
FEV3, VS