Indeed, I did introduce a brief discussion of the vtk pointers in 3.11.2 VTK Pointer Classes in https://gitlab.kitware.com/vtk/textbook/-/tree/master/VTKBook
Also there has been a lot of good discussion here [ vtkNew and vtkSmartPointer](vtkNew and vtkSmartPointer) and here [ vtkSmartPointer and vtkNew in VTK’s API. Best practices?](vtkSmartPointer and vtkNew in VTK's API. Best practices?).