Hello! If there are several changes, keep in mind that this build is done with an AMD card. AMD is fully compatible, and it is not necessary to activate Nvidia drivers. I was even afraid to buy a Vega 56 Asrock because I did not know if that brand would work. I have it working a week ago, and everything perfect, sleep, shut down, restart, double screen, 4K, 144Hz, etc., everything works fine, even the temperature reading that in Mojave 10.14.5 drivers for Vega and the Energy consumption is controlled without additional ketxs.
In devices-properties some variants were entered to inject UHD 630, before I had a GTX 1070 Ti Aorus with High Sierra but not now, and I do not have the configuration of that build.
In summary, I'm not sure for sure that I would change for High Sierra with a GTX. I'm sorry I can not help you, any other query I'm around! Regards.