If we sell a product with OpenCV and it’s dependencies, do we need to make our code GPL?

not true.
you may enhance your opencv app with qt gui, but it’s not a requirement to run computer-vision algorithms

opencv is a c++ library, whatever happens “in Conda environment” is out of control for the opencv devs (not maintained by them).
if conda ships gpl’d components, – there’s your problem
you should probably build (&distribute) your own cv2 to avoid problematic libs