Never was streaming fan ... but decided to give Netflix a try (under pressure from family members)
Here are some fun findings:
Under Edge (both browser and JRiver):
1. Display setting: 4K, Window HDR on - streams in 4K HDR (uses HVEC)
2. Display setting: 4K, Window HDR off - streams in HD max (uses AVC)
If internet is bad, HEVC stream can go down to HD ... but gets back to 4K when internet gets good.
AVC stream never goes beyond HD.
Using Netflix App ... stream is always HVEC ... if HDR is off, UHD content is streamed in SD but in 4k (with tone mapping already applied)
Finally, if you using Edge with display at 4K, Window HDR on ... it will stream in HVEC: 4K HDR ... if you turn HDR off (Win+Alt+B) while Netflix is still open ... stream will remain HEVC, but in SD now ... any subsequent thing you watch will be in HEVC stream but SD ... If you close Netflix and start it again, it will use AVC stream ... its like, Netflix check Edge capability once at start of the sesssion and keeps it for remainder of session (even your display settings change)
Hopefully, this might be useful for someone