The sutil helper library is meant as a simple framework to make the OptiX SDK example code smaller.
The individual SDK examples are normally showing a specific feature of the OptiX API and the surrounding functionality is just there for convenience.
The vector math, matrix and quaternion headers in there are a good starting point. Everything else is specific to the OptiX SDK examples and not really required if you want to implement your own OptiX applications.
If you want to see what is happening inside these helpers and the actual OptiX SDK examples, I would simply build them as debug target and single step through the host side helper functions inside the debugger.
Compare that with other OptiX application frameworks. For example none of my OptiX 7 examples uses anything from the OptiX SDK except for the API headers.
You might also want to look at the other resources inside the sticky posts of this OptiX sub-forum.