Does the shape of your kidneys have any effect on how they function?

Maybe. If they are grossly disfigured or underdeveloped then it is possible that it may contribute to the function of the kidney. There is also a horseshoe kidney which is usually asymptomatic (does not produce symptoms), but a horseshoe kidney can also be more prone to infections. If you have specific questions related to yourself, you should contact your pcp or nephrologist; who can further guide you.
Yes. Evolution has made the human kidney be shaped in a way to maximize filtration surface by placing the filters in the outer surface and a funel shaped medulla where the concentrationg tubules are elongated and very close to each other. It aims to filter more blood and also be able to reabsorve more water.