I wouldn't call it "The best" RTA, but....
If you're learning building, probably THE EASIEST RTA to build on is the Squape R. It's not really a cloud chaser, it only has a single 3.1mm airflow hole (decent, but not HUGE) but it has a swappable deck system and deck design that makes it probably the single easiest RTA to build on. The swappable decks are customized for different style builds. A W (wide) deck for high VG juices and lots of cotton wicking, a D (Dual Coil) deck with separate airflow holes and two juice channels for each coil, a B deck which works like a dripping atomizer where the coil and wick sit in a well full of juice, and the Standard and Curved decks for the old style microcoil with silica wick and flavor wick setups.
All decks have guide grooves to set your screwdriver or drill bit into when you're ready to mount your coil. That takes out all of the hassle of trying to balance the coil as you tighten the screws as well as getting the alignment and height of the coil right every time. The decks are non-conductive so you don't have to worry about shorts if the wires touch the deck.
The W deck is the most commonly used, and probably the all time easiest deck to build on. Lay your bit with the coil on it in the groove, wrap the legs around the screws and tighten, pull the bit out, feed your cotton though the coil and along the same grooves, cut flush with the edge of the deck, fluff and wet down with juice. That's literally all there is to it. It's almost impossible to get wrong.
Even a child could get it right.
EhPro makes a great Squape R clone if you're not prepared to pay for the real thing. (And I wouldn't blame you if you didn't want to drop that kind of cash on an untried RTA).
This RTA has GREAT flavor, and can produce some decent clouds. The largest airflow setting is similar to the Kanger Subtank on the middle setting, so you can lung hit this and it does work with subohm coils, but it's not really airy like a pure subohm tank. It works great with nickel coils as well if you have a TC mod. It's not going to chuck clouds like an RDA made for cloud chasing, but for an RTA it's probably the most flexible and easiest to build on RTA out there.