Let's get straight to it - not a whole ton, depending on the builder. I was visiting a Ryan Homes development in Duncan recently for a pre-drywall walkthrough and spoke with one of the representatives about how the home goes up. As a top production builder, Ryan homes keeps variances and variables to a minimum by using a controlled environment to create the frame of the house in parts. Putting it together is like piecing legos together, and as a result they can guarantee a strong frame (they have a 10 year structural warranty).
On the other hand, a full-on custom builder but on your own land (say, in Traveler's Rest) would be a totally unique build where the design and construction team work together to let you choose every aspect of your home.