When using root access. Call the su binary is the only way?

I don't know if I expressed correctly the question. I was unsure about how to formulate it. You will understand it better with an example.

Suppose I want to edit a text that is out of the application/user scope, for example a shared_preferences file of another application. Can I create a File object pointing to the location and operate with it normally? Maybe do I need to either cp it to a staging location and load it from there or load it in memory using cat?

In other words: Issuing commands to the su shell is the only way to exploit root access?