Let's first discuss what each of these ideas actually are/ represent.
Tip lead- this should merely reflect the degree of counter in the pelvis, relative to the skis. The more counter, the more lead.
Pulling the inside foot back- Again, this is relative to the degree of counter in the pelvis, except in this case, it provides a means of reducing that counter.
When making a high performance turn, there is a certain amount of counter which is advantageous. Too little, and you are square, with limited edging capabilities. Too much, and you are left in a biomechanically weak position.
Sounds confusing? Each skiers body type affects how much counter is appropriate. Women may look very different than men.
Here is an idea-. It requires an 18" piece of masking tape, and a trusted friend, hopefully your size or larger. (Sound kinky?)
Take the piece of masking tape, and stick it on the floor. Put one foot on the tape, with your other foot parallel to it in a sking width stance. With out allowing the pelvis to turn, flex the leg on the tape, while your friend begins to pull on one arm. Attempt to angulate (edge) that foot and remain balanced. You may find it very difficult to angulate the leg with any degree of effectiveness or comfort.
Now, gradually allow the pelvis to begin turning, very slowly, toward what would be considered the outside of the turn. Gradually, you will begin to feel stronger on that leg, increasing the ability to control the "edge". This is what you want to remember!
If you continue the turning movement, past that point of strength, you will feel the leg start to become weaker. The muscles are getting too involved, resulting in a greatly weaker stance.
When we were skiing straight skis, we didn't sustain the amount of pressure for the same time periods as we do now, so it wasn't quite as detrimental to be more countered. But more recently, as the shapes developed and the duration of the carving pressure increased, the better skiers began squaring up up bit more.
This is where the idea of "pulling the inside ski back" came from. That is one way to look at it, but I think you will find that many racers/ skiers think of it more as keeping the outside half of the body moving forward, allowing less counter to occur.
Don't think that the amount of counter or tip lead is an arbitrary amount. It should be only what is necessary.