Suppose: You increase drivers side torsion adjustment (raise driver's front end), What is the effect on the rear? (which side will ride higher or lower?) I know the effect on the rear is slight, but there must be some effect right?

It would affect the opposite corner . One goes up, the other goes down

All sides move a bit, but the opposite moves the most. Raise front left, and the rear left and front right move up a bit, but the rear right would indeed move down. I tell people this every time someone complains about new leafs sitting crooked and they never believe me until they finally try it.