I have been testing the 1st perk in Encumbrance called Balance and Counterbalance. If I understand it correctly, when overcumbered you deal more damage, and when in normal green state, your swings cost less stamina.
I focused on the stamina part, with and without perk multiple times, and it seems that my swings cost exactly the same amount of stamina. Tested on light and heavy attack with all sorts of combinations. Am I understanding the perk correctly, or do you have the same issue?