From Pokémon X and Y onward, if at least one parent holds a Destiny Knot, the baby will inherit five IVs instead of three.
This can be combined with an EV-enhancing item to ensure that one desired IV is always inherited; however, the offspring will still inherit only a total of five IVs from its parents (the EV-enhancing item simply guarantees which IV will be transferred for one of the five that the Destiny Knot allows).
Yes true, but it's a lot faster to just hope the 31 IV is in the right place instead of breeding for the right nature cause you can't give one of the parents the everstone if you use the power items. Power items should be used for ev training and only for breeding if you want to make sure the IV is in the right stat and pray for a good nature or you only want your pokémon to have one good IV then it can be combined with the everstone.