There are several issues going on here........
1st) The air flow screw. When the AFS is flush with the bottom of the base, the unit is wide open. With that being said, the KF feeds the wick using vacuum. The further the screw is turned in the more vacuum is created to supply the wick. The KF can work well with the removal of the screw however, proper wicking is imperative. My preference is to keep the screw flush with the base,
2nd) Leaking from the fill screw. The problem here is the tendency to over tighten the fill screw. What this does is, it over compresses the O ring which in turn causes the leak. The screw only needs to be tightened enough to moderately compress the O ring and thus creating a seal. The compression of the O ring will limit the screw from backing out much like a compression lock washer would do.
3rd) The coil gunkers. Any juice will work in the KF however, the coil gunkers require more frequent maintenance. The use of lower ohm coils will reduce the amount of down time to an extent but, coil gunkers are coil gunkers and the nature of the beast simply requires more maintenance.
4th) Nic levels. The KFs can be as smooth of a vape out there at any nic level however, this takes us right back to proper wicking and the wicking material being used. Improper adsorption and burnt wicking will always lead to a harsher pull. With that being said, for me, I prefer to run with the 12mg juices in my KF's and 6mg's in most every thing else. Once again, Proper wicking and airflow can reduce throat hit and limit the dry hits. The moment you detect a dry hit, most often. a finger placed over the intake(creating a seal) while taking a short pull, will draw more liquid to the coil and wick and thus reducing the harsh flavors.
5th) The filling issue. Yes the top feed system works, however when doing so, any slippage of the finger away from the intake is a case for getting juice all over your table or lap. With the feed screw method your have better control over filling the unit. the key here is to stay slow and steady while tilting the unit to one side and only filling until there is a half moon air pocket showing in the sight glass. If using with the metal tank, it all comes down to experience and feel.
In conclusion, When the KF is properly built and maintained, it is more than capable of producing excellent flavor and very good vapor production.
If you prefer a wide open draw or are in to chasing clouds, a dripper would be the way to go.
As always, your results may very and I hope this helps.....
