Dude, you rock! I love this place and all I am reading!
I have the same setup as you with the ProArt Mobo. The only differences are my 10900k cpu and my old but good 1080ti (which will not work in Catalina).... I am really hoping to use iGpu acceleration on 10.15.5, but am getting a black screen on boot up (exactly when verbose is complete and the apple logo should show up. It seems a frame buffer issue.... Do you have any advice? Much gratitude!