The difference between conceptual design and physical design can be somewhat unclear. Conceptual design usually involves prototyping which is a physical embodiment of the ideas. What is being tested in conceptual design though is the idea or concept, not the specific, concrete elements of the system.Physical design involves more specific detail after the broader conceptual issues have been sorted out.There is a lot of overlap. Think of the trade-off between horizontal vs. Vertical prototyping. Conceptual design can be constrained by physical design when it occurs too early.hat is being tested in conceptual design though is the idea or concept, not the specific, concrete elements of the system. Physical design involves more specific detail after the broader conceptual issues have been sorted out. There is a lot of overlap.