16 lanes total on the CPU, the capture card uses 8, your GPU would probably need 16, then storage, sound, etc still needs lanes.
The thread you found is related indeed, and as Menno said, there is room for improvement, but with not enough lanes on the CPU, that's where I'd start designing a machine.
We're not hardware builders though. I'd recommend following up on this in the Hardware section
with more experienced builders.