+1
At some point we could have higher-level classes that dispatch to the right implementation (such as vtkRenderer etc.), but since we aren’t there yet but dealing directly with the OpenGL implementation, including OpenGL is okay and even necessary in my opinion.
Also, VTK class names usually read left-to-right from more specific to less specific (e.g. vtkOpenGLRenderWindow vs. vtkRenderWindow, vtkOpenGLPolyDataMapper vs. vtkPolyDataMapper, etc.). In keeping with that convention, I would vote for none of the options above but instead propose
QVTKStereoOpenGLWidget and QVTKOpenGLWidget