Sure, there is a relation between height and serves or overheads. The closer your are to the baseline, the more height becomes a factor. There is a difference between a serve and an overhead though. Keep in mind that the serve is the only shot you can hit where you have control of the ball prior to hitting it. This is why it is easier for you to hit it. With an overhead, you don't have control of the ball prior to hitting it. Again, the closer you are to the baseline, the more difficult it will be to hit an overhead.
Here's a good tip for overheads. As you line up for the shot you want to make sure that if you were to just let the ball go down and hit you, it should hit you on the chest. This will ensure that you hit your overhead in front of you and will also promote good balance after the hit.