I did this recently and I wish I could answer you, but I'm on mobile and don't remember exactly what got it working. I also referenced the guide linked below, along with the proxmox documentation.
If you start blacklisting drivers, you've gone too far for passing through Intel quicksync. I think I'm the end it was a pretty basic config, like checking motherboard settings and adding text to the grub config.
Also don't guides say you have to use q35 as the machine type for the VM, but that didn't work for me. Only 440fx works for me.