Gave this a shot on Windows 10. It isn't able to boot into windows after running the script on refind. I eventually got it to boot into safe mode and disabled the dGPU from there. I was able to see my Intel Iris as well. However, I still can't boot with the script enabled so I can't proceed. Going to give it a shot on Win 8.1.
UPDATE!
Confirmed working on Windows 10
So I realized I missed a step before running the refind script! After running this https://github.com/0xbb/gpu-switch (I had to run the newest version as the old one wouldn't launch) and then rebooting with the refind script, I was able to detect my Intel Iris and get gpu output on Windows 8 and 10. Thanks for this guide