The video encoder block is always the same (when present) on a generation of GPU's. So all Pascals have the same encoder block, all Turings, etc.
I know nothing about the AMD GPU's, but on the Nvidia side you've been able to use Shadowplay for low-overhead streaming and recording using the NVENC hardware encoder for many years now going back to the Kepler generation. The quality of the hardware encoding used to be much worse and has steadily improved every generation to the point where you can now use Shadowplay for both streaming and recording with very good quality, comparable to x264 run on the CPU.
Oh I see. There doesnt seem to be many benches out there.