After many rewicking and recoiling of my Kayfun, I finally found a wicking method that does not leak (for me at least) when using different PG/VG ratio.
1) I made sure to have at least 2mm of space from the air vent and the coil.
2) When wicking cotton, cut exactly the height from the coil and the juice deck.
3) Flatten/paint the juice wall with saturated cotton on both sides.
Final product:
Not a drop or leak:
P.S. I always top fill plugging the air hole slowly pouring juice before the threads, put the top cap back on, turn it upside down and blow through your drip tip with a piece of tissue to catch some juice
