From what I have read on the wiki, fists are NOT affected by Strength and are also NOT affected by the Slayer perk (+30% attack speed) and their maximum damage is 5,5 (http://fallout.wikia.com/wiki/Unarmed_damage).
Using bare fists is therefore not recommended, even with the unarmed moves. Don't know how a power attack or charging attack bonus damage is calculated, but it's probably just a multiplier.
I would personally LOVE if some perks would make your fists into a viable weapon - Adamantium skeleton could add bonus unarmed damage if you're using your fists (your bones are ADAMANTIUM after all).
Nerd rage could also add bonus unarmed damage while using fists and raging.
I realize that it probably won't be implemented, but as the devs read this forum I would love it if the sequel would allow a player to not use any weapons and perhaps not even armor while still being able to do a good enough amount of damage with the right selection of perks. Naked ninja ftw!