@buddyjack2,
For systems that have dual GPU configurations (dGPU + IGPU) like yours we generally recommend enabling the IGPU in your BIOS and configure the dGPU as the Primary. Then use WhatEverGreen to configure the IGPU with a "Headless" PlatformID and use a SMBIOS that supports dual GPU configurations which in your case (Kaby Lake CPU) would be iMac 18,3.
Genuine iMacs with dual GPU configurations use a Headless IGPU PlatformID in order to be able to use IQS and other IGPU related features.
See
Headkaze's guide if you already understand IGPU PlatformID's and Device Properties or the
Lilu + Plug-in's guide if your new to it which has a dedicated section on Headless PlatformID's.
Cheers
Jay