The first thing to do when setting up to hit a long club is to set the face behind the ball aimed at your target. You should also focus on “soling” the club flat on the ground so that neither the toe or the heel are up off the ground (see photo below).
From there you have set the club, commit to it and now “measure out” so that your body is the appropriate distance to the ball with a good athletic and repeatable posture.
Finally, regarding ball position, this is a preference not an imperative. The driver ball position is the most forward, generally opposite the forward foots instep (left-foot for right-handed golfer). You can progressively move ball position slightly back as the club gets shorter so that a mid-iron (7-iron) is in the center.
Besides a few common rules of thumb, it really is best to have your PGA Professional check your setup from time to time and if they make a recommendation, try to create an awareness of what feels different compared to your normal so that you will implement it on the course.