You are free to get what you like; but personaly i would recommend THR Kayfun lite plus Atty. If you want a Lung hit option later get a few Kayfun Monster V3 bases, O rings, a few glass replacement tanks a few barrels FT calls them graphic tubes. A few chimneys. If you want an Atty that holds less liquid get the nano chimney and bell caps.
I say this because i only have one complaint about the Kayfun Mini V3. Its a great Atty but it is top filled, and if mine sets a day I have to close the juice Control or i come back to a puddle of juice just because the O rings On the drip tip are weak and don't create a proper vacuum.
You wont have that problem with a bottom filled Atty.
Other bennefits of older tech.
1. The full sized Atty holds more Juice. The Kayfun Mini V3 only holds 2 ml.
2. The replacement parts for the full sized Atty is much more abundant ie the O rings, screws, barrel, chimney, top caps, bases, etc.
How could the drip tip o rings affect the vacuum?
I'm not saying you're wrong, because I'm pretty new to vaping, but I don't understand what the drip tip o rings have to do with the internal vacuum inside the tank?
I can pull my drip tips right out out and my tanks don't leak.
Anyway, not taking away from your experience with the Kayfun Mini v3, but mine has been different (mine is a clone from ebay).
I did initially get some leakage through the air holes, but this turned out to be user error (I wicked it incorrectly).
Since I have learned to wick it, I have had no leaks whatsoever.
I mostly use mine on the weekends in conjunction with my Endura T18.
I use my bigger setups during the week, but at the weekends when I'm out and about, I like the small size of the T18.
This means that my Kayfun Mini v3 sits for five days out of every seven loaded with juice and unused. It never leaks.
One thing that I did discover is that when I first filled it, a tiny bit of liquid would find its way into the air holes. Not enough to leak per se, but enough to make it gurgle a bit.
I found that I could eliminate this by inverting it after filling and opening the juice control while the tank is upside down.
The only other top fill tank I own is the original tank that came with the Endura T18.
I no longer use this tank, but I did really like it. The top-fill was really convenient, and it never leaked.
The only reason I stopped using it and bought the Kayfun Mini V3 was that I didn't want the ongoing hassle and cost of buying the coils.
I figured that, since each pack of five coils is around $12, I might as well just buy a rebuildable tank for about the same price as two packs of coils.
I'm not saying that top-fill tanks never give problems, but my experience with these two tanks has been very positive.