I think the old rule of thumb was good duck tape, 5 layers equals 1*. Wag, a credit card is probably around 1*, others may know better.

Correct. Some people are uncantable, can't tell you why, just doesn't work. If it hurts , it's wrong.

If you are knock kneed due to flatfoot(tibia rotates internally when subtalar joint pronates) an insole will help correct it.

If you are knockkneed due to a hip or knee issue, outsole canting(or...

In boot shims address the foot. Under binding and under boot shims address more proximal biomechanics.
Apples to oranges.