I am surprised that the Neo G9 won't go past to 12bpc greater than 120Hz. If it helps any, I am using this HDMI 2.1 8k certified cable:
https://www.amazon.com/dp/B08P5PPWRB?psc=1&ref=ppx_yo2ov_dt_b_product_details
Nice setup you have there, btw. I am waiting for a good price on a 4090.