Sorry, but this is not how it's supposed to be. A new device, with nothing installed on it should work near its optimum performance.
I don't have time to spend tweaking and researching tips to fix something that is supposed to work from it's factory default state.
Let's say I do all those those things, in a couple of months Windows will still slow down and become loaded with background processes, as it always does.
Also, why should I use MS browser, I want to be able to chose which browser I use?
Sure, if I keep CPU + GPU at minimum performance, shut things down and keep display brightness at 10% I probably will squeeze some additional hour or so, but this is not the point with a high-end device, is it??
Another thing: it's the end of August and I still cannot install the May 2020 Windows update (2004). I mean this is ridiculous: the latest Microsoft device cannot install the latest Microsoft update!
Does anyone actually use these tablets at Microsoft?? Are they happy with them? Cause I surely am not.