I only use 3mm screwdriver for the last 3 weeks or so and it works great. I use Koh Gen Do to wick it. What I generally do is getting ris of the most one or two layers of the cotton, then cut 2 thin strips. I learned this from qorax and basically by using this method you have 4 cotton tips right on top of 4 juice channels and it wicks perfectly.
For the last week or so I have been using 100% VG only - no dry hits or anything. My airflow is not loose but not too tight neither. I do not know how to explain it

All I can say is you can't lung inhale it the way I use it.
The only problem I have at this moment is that Boba's Bounty basically kills the coil so quickly. Seriously, you can't even rewick it without changing the coils every 5-10ml or so. I had a 50/50 pg vg where I had to rewick it every 15ml and build a new coil every 30ml or so.