Good infoGenetics is the number one factor concerning performance. Management is secondary.
I do not buy into the excessively high protein % methods. I have weighed a lot of growing birds, and there is a point where money gets wasted. 24% game bird starter is not unrealistic up to 8wks, but more is a waste.
Keep in mind that some recommendations for more is for birds on low protein forage. You might be feeding them 30%, but they are not taking that in.
Young birds running all over the field after pullets will not get excellent rates. I prefer them to be confined up to 6-8wks, at which point I separate them, and put them on "grass". From that point on, I want my pullets raised differently (and separately) from my cockerels. There are no advantages, and only disadvantages to pushing pullets. Manage them well, and let the genetics talk.
Chicks use up a lot of energy to stay warm. Keep them warm a little longer if the rates matter to you.
You would be surprised how much improvement can be had from management alone. It is a series of small victories, and not one big one.