Some people seem to restore the giant shark C.megalodon as a more bulky scaled up white shark.

However most modern day sharks are far less robust than a great white, even ones that are larger in size (whale shark and basking shark).

Do we have any evidence that it was indeed similar in shape to the great white?
(Besides having similar teeth, which could be  because of similar prey)

It's actually uncertain whether megalodon and the living great white (C. charcarias) are closely related or not. Some research suggests they are, in which case it is reasonable to reconstruct megalodon as a larger version of the great white. However, a recently discovered well preserved head and vertebrates of a 4 million year old great white suggests that the great white may have evolved from something similar to a mako shark. This would mean that C.megalodon and C. charcarias independently evolved large body size, but could have been of quite different overall body shapes!