1. K4 is definitely airier than the Erlk. Nearly one & a half times
2. Erlk is twice airier than the KFLs (with the ODPP and AFC removed)
3. In today's parlance I fully recommend getting the ODPP (Open Draw Pos Pole)
4. If you are onto DLH that 2.2mm ODPP enables it perfectly
5. O-rings are outright expensive in the Erlk webstore, get them from the link in OP
6. Don't bother with Erlk OEM glass tanks (21mm), they'd break before you say John Doe
7. Get the 22mm IBT ones instead (you have color choices there too)
8. If you like the Poly tank (I do) grab a few from Erlk store. You'll not find them elsewhere
9. Erlk performs perfectly under all Ohms, juice viscosity and wattage (I've tried them all)
10. Erlk stock DTs are narrow. Use a li'l open bore ones (eg. Old Sam) and you've a perfect vape there.
Congrats on you decision! Erlk is still my best atty