I don't believe doing PE while you're still in puberty will affect your gains in a magic way...you are born with a specific size...just like height...i don't know if it's true but i have heard you develop these things even before you are born,you will have a specific height,hair color,penis size,etc.And you cannot go pass that,naturally.I mean if you're born to be 5'7 , you won't go pass 5'7 no matter what you do.That's your limit.Same thing with penis size.If you're born to achieve 6 inch by maturity,unless you do PE,you won't go pass that size,naturally.Doing PE while in puberty won't enhance your true size,it will add to it.In my opinion it doesn't matter if you do PE at 16 or at 30,you will gain the the same.
The best way to maximize and reach your full body potential is to make sure you generate enough growth hormone.Good diet,good sleep ( at least 7-8 h at night ),exercise,etc.There are tons of methodes to maximize your growth hormone realease,from some specific sounds ( you listen to them while you're sleeping and you generate more GH ) to GH supplements.
Some will stop before reaching their full potential because they have an unhealthy lifestyle.If you're full potential is 6 inch and you eat McDonalds,sleep 3-4 h a night,don't exercise , etc , etc , you might stop at 5 inch or 5.5 because you're body didn't had the resources to grow further.
This is just my opinion, right or wrong.
I grew up in the '70s & it was cool to smoke & I started young. During puberty you need nutrients from the food you eat to develop & grow. If these nutrients are diverted to repair the damage to your lungs from smoking you're not going to receive all of them to develop.Just before I turned 13 I started puberty. Like most young boys I was fascinated with my dick. It was my favorite toy. I remember measuring it at 13 & I was "6 1/2 length nbpel. At 21 I was "7 5/8! I'm sure if I didn't smoke I'd've been larger.