Thanks Sholander for letting me know about netflix specific bandwidth test fast.com. I was not aware of it.
I did lot of test and measurement of the netflix over kodi and Edge (both on 1080p). When the lagging issue appeared (which I can almost always reproduce in Lucifer S04E04 time 6:30-7:00 ) there was a higher bandwidth demand (based on my router/netdata monitoring). Usually it is about 10 Mbit/s, but during that critical time the average bandwidth was about 13 Mbit/s with peak about 40 Mbit/s. I executed the fast.com during lagging and it gives about 40 Mbit/s (with 8 parallel sessions). So there shall be enough bandwidth.
When I watched the same episode with the Edge (1080p), there was never ever an issue. The bandwidth demand from Edge was little bit higher, but no lagging at all.
So my conclusion is that the used InputStreamAdaptive has worse buffering than used in Edge implementation of Netflix. With that I’m considering to by Chromecast with Google TV with native Netflix app.
I can of course use the suggested VP9. There the requirement bandwidth is much lower, about 2Mbit/s. But I’m afraid of artefacts. With the fiber link I expect the best service.