For the iGPU issue, there should be an option in your setup utility/BIOS on your motherboard that either allows you to disable the iGPU entirely (usually in the settings for CPU or chipset, can vary from board to board), or (in the case of my Asrock board at least) there is a “dGPU only” mode that automatically disables the iGPU when a dGPU is detected. For the RGB, since the 9070XT is a partner only card (so many different manufacturers make them), the RGB implementations can vary a lot between models as there is no standard design (would be wise to edit your post to say which specific brand and model of card you have in case other people with that brand have experience with it). It might be worth just installing openRGB anyway and seeing what it detects automatically, as it could pick it up.

Same on AMD as well. vaapi acceleration, after installing the appropriate packages, works nearly flawlessly on all brands of GPU I have tried.