Well, I am a RTA user. My experience comes from using: mini protank II, CE4/CE5, Kayfun lite, Fogger V4.0, Squape(v1), and an Aga-T2+.
1) I like the squape(v1) the best, and it's the easiest to have and maintain by far. The downside is no adjustable airflow, airflow comes from the 510 screw, and it's big. the plusses are pyrex glass, 5ml of juice capacity, no tools needed to refill or rewick, I'd suggest that, but you might have a lot more support with a Kayfun at the moment.
2) I am currently vaping almost %100 VG juice. I prefer cotton with high VG, since you can lower the density of cotton. VG wicks better when the wick is not as dense, and the thickness won't let it gurgle as much. when they say less is more, that's true with VG. with PG though, I would go for quite a bit more density to hold it in and not get as much gurgling. The best way I can explain it, is if you have a mesh strainer... like a mesh sink strainer... put one drop of vegetable oil on the mesh, and it won't go through. put one drop of water on the mesh, and it will drip through. Same goes for the wicking material being suspended over the airflow.
I'm one of the few RTA users that are semi anti-kayfun. It's an ok system, but it has it's limits. There are easier tank systems out there. IF you're looking for a bottom feeding RTA and using a high VG based liquid, look for big juice wells. Also, keep in mind that some juices will crack plastics, so I tend to stick with glass only. Kayfun IS a good atomizer, it's just not the best IMO. For a dual coil, I'd recommend getting a fogger V4.1. My fogger tends to dry hit usng higher VG based liquids, but that should be fixed int he V 4.1. I'd probably start off using cotton.. only because you can manually monitor the density. Once you know the density that works best for your juice, then you can look into getting alternative wicking material. Besides, cotton is cheap... like $3.00 for a year supply of organic cotton.
