The only way I found to actually get 1080p for all content on Netflix on a PC was to use the Windows 10 Netflix app. In any browser, some of the content would be 720p or 480p otherwise. Edge gave 1080p sometimes, but Firefox and Chrome maxed out at 720p in all cases where I looked at it (Ctrl+alt+shift+D to see the actual resolution).

And then there is 4k, which is limited to certain intel chipsets.

That can’t be right, I’m fairly certain I tried 4K streams on my work / home iMacs (5K) and on my MBP (3.5K)

Their "System Requirements" doc says 4K is only available on Windows, and only with Edge:

https://help.netflix.com/en/node/23742

It is possible that doc isn't kept up to date though. :)

I don't want to advance anything (don't have time to find the source), but I think Apple have something special built in Safari/Webkit for Netflix. That relate to decoding, quality and battery combustion while streaming.

Safari & Edge support a more advanced version of HTTP Live Streaming (it's the same tech Apple uses for their event live-streams) plus the DRM scheme Netflix uses.