The TS4 is definitely not for those with lower swing speeds! If you are looking for a Titleist driver designed for slower swing speeds, try the TS1.
Don't try to pick a ball based on swing speed. That is pretty pointless. If you hit 50 full shots during a round, none of those shots, even with the same club, with be made with the same swing speed.
Pick your ball starting at the green and work back. Pick the ball that feels and performs best for the scoring shots. All the balls in the Titleist line are within 3-6 yards of each other off the driver.