Bows always shoot best at peak weight- The limbs have the optimal load, the cam/cams ar ein optimum position, and generally they are more quiet and will shoot with a more "tight" feel (less vibe, etc)

You may or may not have to re-tune, most likely will at least need to re-adjust your sights a bit- depends totally on your arrow/arrowspine. If you are using a drop-away it may also affect the rest timing.