Sorry if I wasn't clear. Cinema 4D Python does not come with setuptools or pip installed you have to do it.
My point was, PyCharm automatically do it as long as the defined Project Interpreter is c4dpy.
Just a quick overview:
In Pycharm go to File -> Setting (CTRL+ALT+S)
Then Project Interpreter
In the top, click on the bolt button and Add
Make sure to rename c4dpy.exe to python.exe (Pycharm do not support something not called python)
Then define the interpreter as python.exe (our c4dpy.exe located in our Cinema 4D installation)
Click Ok, Select it in the dropDown list, it should load a bit (installation process for pip and setuptools) Then click apply and pip/setuptools is available. You can also search for any package available from pip which is compatible with our version of Cinema 4D by clicking on the Green addition sign.
With regards o your question, yes python installation directory is C:\Program Files\MAXON\CINEMA 4D R20.038\resource\modules\python\libs\python27 but you should never modify these files. And we are not responsible for any issues related to any modification of these files.