Maybe our definition of a loose draw is different. To 'me' a loose draw is when I don't have to really drag hard and still get a good vape. A tight draw is when I really have to drag/inhale hard to get a decent vape.
I'm not saying that's the right definition, but that's how I've always thought of a tight draw/loose draw. The cone/adaptor will make the draw tighter/harder because it blocks the air holes in the cartomizer.
To get a better vape- try low resistance cartomizers. Boge 2.0 or Smoktek 1.7 are good. Dual coil are OK IMO but if they are hot and depending on your juice-if it's a light flavored juice you won't get quite as much flavor. Some juices do hold up to dual coil cartos.
I'd try getting lower resistance cartomizers and possibly increase the nicotine content. TH is all about the nicotine. More PG increases TH somewhat but it's mostly about the nicotine.
You said you're really screwing the carto on tight. That could also be a problem. The button gets pushed down on the battery when you do that. You could get a tiny screwdriver and try to put it in the center hole of your cartomizer and pull it down a tad.