How does the feat Hand's Autonomy work with Twf, end result penalties? How does it interact with other ways to reduce TWF penalties like the Perfect Balance Fighter ability?
If you're using TWF, hand's autonomy and are fighting with at least one light weapon with no other special abilities applicable then the TWF penalties are -1/-1.
At 15th level, the penalties for fighting with two weapons are reduced by an additional –1 for a two-weapon warrior. This benefit stacks with improved balance. If he is using a one-handed weapon in his off hand, treating it as a light weapon, he uses the normal light weapon penalties.
At 11th level, the attack penalties for fighting with two weapons are reduced by –1 for a two-weapon warrior. Alternatively, he may use a one-handed weapon in his off-hand, treating it as if it were a light weapon with the normal light weapon penalties.
You reduce the penalties for fighting with two weapons (including fighting with double weapons or when throwing weapons from each hand) by 2, to a minimum penalty of –1. This benefit stacks with the Two-Weapon Fighting feat.
Perfect balance stacks with improved balance but not with hand's autonomy. It would stack with possessed hand. Perfect balance effectively removes the penalty for using TWF, assuming you use at least one light weapon. If for some reason you want to swing a couple of scimitars or something around (w/out effortless lace) then hand's autonomy can stack I guess, reducing the penalty to -1/-1.
What about the iterative attacks from improved and greater TWF?
Let's say your bab is 11, and you take the seccond stage of TWF. normal penalties would be -2/-2 , -7/-7. Could I stack these reducers for the seccond set of attacks, say bringing them to -2?(if I head enough effects)
The -5 on ITWF isn't subject to being reduced any more than the usual penalty for the 2nd or later attack by BAB is. Perfect balance and hand's autonomy both talk about the TWF penalty - not the penalty for ITWF or GTWF.