They're artificial, though in general they're no longer based on humans. They have bio-machine components, sort of synthetic materials that act like normal organic ones, though they're created, instead of grown.
They approach problems by analyzing it beyond the point where it needs to be, though that only applies to problems that can be solved scientifically. When analyzing new technology, or new materials, they break everything down into its constituent parts and go about basically simulating everything that could possibly be done with it. Of course, it mostly fails to produce anything, but it means they never miss an opportunity to advance.
The social contract thing is a concept in society where you agree to abide by the rules implictly. The Var state their social contract explicitly, sort of like laws, but with the ability to opt out of the Var society, though that basically means leaving Var space, and being disconnected from their society.