I rarely hit 100% on any shot except some first serves. I interpret hitting 100% to mean as hard as I possibly can.
On the other hand, I have been spending years drilling nice high racket head speed topspin fh and bh shots. The fast swing is crucial to imparting enough topspin to keep the ball in the court. If you don't take the cut at the ball, your consistency will go down. But make sure that the cut is balanced and not as hard as you can possibly hit. The more athletic you are, the easier this will be. I'd say shoot for 70% up on the average rally ball.