The 1st approach is to spoof the VESA driver so system will boot, but you need to fully disable it after you installed the OS. You still need to patch for USB, graphics, audio...etc. etc.
The 2nd approach, you're able to disable the discrete card with SSDT-5, but you still need to include the other SSDT where the _OFF method is declare which you included in SSDT-6. What you should have done is just add the patched SSDT-5, enable autoMerge, but don't drop the OEM. You still need to patch the DSDT for USB, audio, graphics...of course that could be done in the Config too. You'll also have to use the rename of GFX->IGPU, HDAS->HDEF...etc etc.