At the moment, someone else testing brought up some issues with the automated app that he and i are working through.
If you are following the youtube video, then it will not work. The youtube video shows the output from the app ( the code that is making the modifications is running in the background in the video)
If you try to run the commands from OS X, this will fail. the EFIVARS partition is not available from OS X in any regard.
If you are having GPU issues, then you are going to have a difficult time getting into OS X in most cases beyond Safe mode. Safe mode does not load the AMD GPU.
for the record, the automated app is tested on nothing but a VM, and one MBP at this point. There is a very low chance it will be a fully automated solution at this point. Further development is required.
You may be better off just following the current tutorial, which will produce a working machine, rather than this project which will require debugging at its current stage.