If you have an HDR compatible TV and the most recent version of your TV vendors Netflix app you will be able to stream in HDR. Tried it this morning on my 55x8500C. This is not really an HDR panel but there was minor improvements to picture quality I feel like. When you click the title the TV jumps into HDR mode (for any resolution until it ramps up to 4K). I'm interested to know if even the 720P stream is HDR10.
Marco Polo is the only title currently streaming in HDR.
I'm sure with an OLED it would look much better.
I think I'm more interested to see films in HDR as TV shows aren't as cinematic.
I would say that Marco Polo in 4K more feels like 1080P as it doesn't seem to resolve any additional detail. I'm not sure if that's down to camera work, lenses or just the nature of 4K film compressed to be streamable