Glad you are making progress
Sorry, I didn't mean to suggest you were unable to understand, only that it's just a matter of reading-up on the successes others have had before us. Many people will tell you the NoVPAJpeg kext is not good because it renders JPG files in software rather than hardware, so misses-out on a lot of the available power in the iGPU. This is true but as you found, getting the iGPU working in what they call "headless" mode is sometimes not so straight-forward with sections of a BIOS becoming invisible unless you activate a certain setting or two. What you need to change is basically not there.
Yes, rendering videos in Final Cut
might be affected by this workaround because it uses software rendering for some file-types. Once you get the time, read-up on how to activate your iGPU as headless. As
@Big-W said in post #66 you need to find the settings to change the memory allocated to the iGPU. They are there, just buried right now.
If you can mount your EFI partition to access the
config.plist there should be no reason you have a privileges problems. While it is mounted check it with Disk Util, First Aid etc.