[el Filou]

DXVA2 Native gives blurred chroma on NVIDIA cards, so to get the best quality other decoding options are better.
If you only watch HD I would use DXVA2 Copyback (it gives deinterlacing artefacts with 576i on my setup, but not with 1080i), or even software. Try to compare both while watching CPU and GPU clocks and %age utilization, software will use the CPU more but H.264 L4.0 is really easy to decode on a modern CPU, DXVA Copyback will use the GPU slightly more with madVR but with 720p/1080i it should be hardly noticeable.

You say you're watching on a 1080p TV but then you talk about a 4K 75" one? Which is it?

madVR has "reduce compression artifacts" (in processing => artifact removal), which is self-explanatory. If you use it in combination with NGU sharp you also gain some processing time.
I've found that with HDTV, "reduce banding" is useful too, I use it at low setting, and previously when my cable provider was stuffing too many channels on each mux sometimes I had to push it to medium (I mapped it to a keyboard shortcut and only increase it when I notice too obvious banding in the content I'm watching).