2. The categories Visceral Design, Behavioral Design and Reflective Design are all important because they all can be used as a tool when analyzing a product. On top of that all these categories are true, for the most part, of how a consumer views a product. I think these three categories could have better names: Visual Design, Performance Design and Self-Image Design respectively.
3. The best way to decide whether Visceral Design, Behavioral Design and Reflective Design are most important for a product is to analyze the product itself and to decide what the consumer will look at the most when shopping. For instance, a clothes designer should consider Visceral Design and Reflective Design the two most important because when people shop for clothes they care most about how the clothes and how they will make them look. On the other hand, when a designer is designing power tools they should consider Behavioral Design first because when people buy power tools they care about usability the most.