I've heard that the Lemo is good but haven't tried it yet myself. The Orchid is also pretty good, but not the same as an RDA.
The Lemo has incredible versatility with the airflow.
All the way open is about as close to a dripper as you can get. All the way closed is like trying to inhale a sofa through a straw. Some folks have an issue with the flow controller ring readjusting throughout the day, but a small o-ring (like off a drip tip) placed around the bottom solves that.
The Orchid I use is a V4 and while it doesn't have adjustable airflow, the stock flow is still very airy. It's a bit tighter than the Lemo.
Personally, I'm not a huge fan of that Orchid. I find it finicky to wick, and prone to leaking when filling. Since I've got a Lemo, it's been shelved. The Lemo has none of those problems.
I have an Atlantis, and wasn't thrilled about not being able to rebuild it.
The Kanger Subtank takes replaceable heads, but also has a rebuildable deck you can use if that's what you prefer.
You'll find tons of opinions here about Atlantis vs Subtank, I personally like the Subtank of the two. I seem to get better flavor and airflow from it.
Past that, I still prefer the Lemo over both of them. It's much more versatile, smaller diameter, has a better build deck, but holds 1ml less juice than the Subtank which holds about twice what the Atlantis does without the extended tank.
As a side note, Kayfun's have a notoriously tight draw. The V4 is a lot better than the previous versions, but it's still really tight.
