How do they work alongisde Destiny Knot?

I'm asking this because I have noticed that it's easier to get a 4-5 IV poke when I'm using a Power Item. Does this mean that the IV passed down by the Power Item holder isn't counted in the whole "5 IV from each parent" calculation of Destiny Knot?

I have also noticed that Evestone now seems to affect as well the Gender ratio, making it easier to get children with the same gender as the holder.