Get a Squape R.
They're extremely easy to build on. By far the easiest RTA I've ever used. They hold 5.2ml of juice. They come with several swappable decks including the W (wide) deck that has extra wide juice channels for high VG juices. You'll have no problems with dry hits or burning, even with a 100% VG juice in this tank. The deck is non-conductive and there are guide grooves on it to lay the tool that your coil is wrapped into which means you always get the perfect alignment and perfect height off the airhole for your coil. No fiddling around with trying to balance the coil and tool above the deck while you try to secure the leads like a Kayfun/Lemo style RTA. They work great with nickle wire coils too.
Wicking is near impossible to get wrong. Feed your wick through the coil and along the alignment groove, trim so it's flush with the deck, fluff the ends, and that's it. No worrying about blocking the juice channels, no fiddling around with trying to lay the wick just right, no worrying that the chimney is going to pinch off or move the wick when you screw it on, it's super easy.
Plus you can remove the deck while the tank is full, and the tank is glass surrounded by a metal sheath. You fill it just like you fill the Aerotank or Nautilus. Like I said, it's by far the easiest RTA I've ever used, and I've got three Kayfuns that are now going to be boxed up and put in a closet because they seem absolutely primitive compared to the Squape R.
Here's an example...
Coil build on a Kayfun/Lemo/Similar RTA deck:
And here is the Squape R:
And like I said, there are multiple decks that are easily swapped out. Just remove the top screws and pull the deck off and click a new one in. There is the standard deck which is best for thin juices, a C (curved) deck which is for longer wicks, a W (wide) deck for high VG juices, a D deck for dual coil builds that has two alignment grooves, a set of juice channels for each coil, and an air hole under each coil, and a B deck which works like a dripping atomizer where the wick sits in a pool of juice. The EHPro Squape R clone comes with the S, C, and W decks, and it only costs in the $35-$40 range.