I would argue a good chunk of your extra distance is only because more modern irons are much stronger - a 6i of yesterday has the same loft that a 7i does today, for example.
The cavity back irons will be more difficult to work a draw/fade than, say, a forged blade. But you gain the forgiveness. That tradeoff still exists - workability vs forgiveness. You have to figure out where you want to lie in that trade off and then get an iron that matches. That being said, compared to older irons, I think nearly all irons today are more forgiving and less workable than their older counterparts (old blade vs new blade, old cavity back vs new cavity back).
Shaft flex is a tradeoff between distance and control - basically, swing the weakest flex that you can control. The other reason to splurge on a shaft is for consistency in how it load/unloads. I haven't really researched graphite shafts in quite a while but I imagine they are generally lighter in weight for the same flex so if you like lightweight feeling, graphite makes sense.
I don't care if I'm playing with a 110+ golfer - you can suck and still play fast, it's just about being aware of yourself and others.