The general goal in simulation is to reproduce reality to some extent with minimal effort, and this approximation should serve to be your concrete goal of designing a robot or evaluating the performance of existing ones.
Digital models are an abstraction of reality. You don't need to reproduce every detail of the physical robot in its Gazebo model. If you tried to do so, the required workload would be so high that the benefits of simulation would not compensate for the effort. Instead, what you do is reproduce those characteristics to verify the robot. You should start by defining the concrete goals and then build the simplest model that will allow us to comply with them.
Let's go through an example ...
