Thanks for the thorough reply.
The Testing Lib you mentioned helps a lot.
Regarding the first part:
Simply put: I need a simple solution to pass Rhino Geometry from the GH environment to the cpp side, do some processing of the geometry there, and pass some geometry back.
For this, unless I miss something, cannot be done easily and universally for both Windows and macOS platform. (If using McNeel’s solution, this need C++ SDK for macOS?)