IMO none of the joints should ever be 'locked' or fully extended. Locking a joint is akin to tensing a muscle. Both will impede the transfer of force to and from the ground. When a joint is fully extended, it must retract again to re-open the path. Likewise, when a muscle is tensed, it must be relaxed again begore it can contract appropriately. IMO, the range of motion should be to near full extension and the extending limb should be relaxed and supple. The power should always be there are a moment's notice if the body is aligned properly, the intention to use it is there, and the timing and positioning are advantageous.

Long power is not dependent upon the elbow being locked out. Long power (and short power) is determined by the intention driving the body's alignment. Long power and short power are not exclusive to only certain physical postures.

I practice with both light contact and medium contact, usually to the sternum/torso and legs. Contact to the face, head, joints, and throat is usually very light (placing the hand) followed by a little pressure so my partner is aware of the opening.

Dzu