HI Small Fry 
In Carrara, you have three different scene scales, Small, Medium, and Large.
Small is ideal for making small scenes like a product box shot,
Medium is for working with Human scale figures , and Large is for big landscapes.
With each scene scale,. the camera motion scale is changed to allow you to move around easily, ..also the basic scales of objects you add will be smaller or larger depending on the scene scale. (inches, feet or Miles)
All of the example scenes, use elements which can either be created in Carrara (in any scene), or can be saved in the browser, and loaded into another scene.
Things like the Background or Realistic sky, can be saved and loaded, and aren’t as scene dependent as an object or figure.
If you’re working with figures,.. start with a Medium scale scene load in your figures and add the background or sky you want from the browser,.. you can still add a Small object, or a Big terrain to that scene..
You can also work in Carrara with multiple scene files open at the same time.
this allows you to Copy / Paste items from one scene, into another. but it won’t change the scale of them.
Finally, you can change the scene scale in the General tab (top right) when you select “Scene” in the instance list.
this doesn’t rescale any objects, but it allows you to move the camera in lager or smaller steps.
hope that makes sense
