When choosing settings for each of the building performance factors, should you always choose the setting that gives the absolute lowest predicted energy use?

You shouldn't because sometime this action could be illogical or unpractical. Also, sometimes we have to take into consideration the different goals of the client which might not align with the lowest predicted energy use.

How can you use Insight feedback to make design choices regarding materials, lighting, PV, etc.?

Insight is a good interface on a high level for making design choices regarding different materials because you can see how different variations would affect the different goals you have for the building design.

How can model-based quantity takeoff improve the design process?

Model-based quantity takeoffs allow for highlevel estimation that can inform the design process becuase the process is easily adjustable for different design iterations. With these rough estimates, you can also see what components to the building are the most expensive/most labor intensive and more easily sample different materials to adjust these factors.