Yes, it is always useful to use them.
Good organization skills go far in modeling.
Because north angle (for shadows) is based on global axes, you don’t really want to move the model to the axes. Moving the axes is better idea since you can always reset it to the default (starting point). As differet terminals would have different logical axes, you can assign different axes in the components or groups.
Every case would be different. but you would need at lease several groups and components. To me, the most logical thing to do would be to have different blocks/buildings/terminal in different groups.
There isn’t really a fency tool for this purpose. A good use of all native tools in SketchUp will get you there.
There is a limit on how much pixels your image can show in SketchUp.
As SketchUp versions up it seems like the value changes. So I actually don’t really know the actual value now. But if you check “Use maximum texture size” in Preferences/OpenGL, you should get more pixels visible granted your original image contains that information.