I'm reminded of when OneDrive online was super slow on Linux but fine on Windows on the same machine.  It is possible it's just an accident but I think in this case, the cause runs deeper and can't / won't be patched quickly, so it doesn't look good.

Especially what's happening with the performance on YouTube outside of Chrome, very suspicious. 

Yeah that I can attest to personally.  General navigation of youtube on my (admittedly not very powerful) N3350 in Edge is insanely slow, it's actually embarrassing and borderline unusable.  Other websites work perfectly respectably so intentional or not, it's really not making them look good and they need to do something.  Funny story, I have to use Edge though because their own browser doesn't support the tricks Edge does to make playback possible.  I can watch 4K60 VP9 without a single dropped frame in Edge but Chrome struggles with 1080p30

i5-8520U, sometimes takes even 5 seconds for text to catch up in the search bar on YouTube. All the suggested videos and comment sections also can take upwards to 10 seconds to load. And people were upset that Microsoft was constantly pushing Edge? Well it looks like Google is going the passive aggressive route in pushing for their browser because who doesn't use Google Maps or YouTube?