Don’t forget any path. To use my own python binding I use
import os
os.add_dll_directory(r'G:\Lib\install\opencv\x64\vc15\bin')
os.add_dll_directory(r'G:\Lib\install\vtk\bin')
os.add_dll_directory(r'F:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v11.2\bin')
os.add_dll_directory(r'F:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\v11.2')
import cv2 as cv
check this issue too Python Bindings importing error · Issue #17632 · opencv/opencv · GitHub and the reason is discussed here Issue 36085: Enable better DLL resolution - Python tracker