Thanks for the questions!
It works best with bright stuff, I’d say. I watched The Witcher and in dark scenes I often just guessed (and listened to) what was happening when they might from outside got moderately bright, while there were some desert scenes that were surprisingly easy to see even when the sun was shining outside and the kitchen was relatively bright.
When I was sitting down to eat, I would often just put the dark front thing on the glasses, with that I didn’t have major issues (although if it’s very bright, on some angles I can get reflections on the screen), but of course that’s not quite AR anymore 
It also depends a lot on how bright whatever is directly in front of you is. I was positively surprised on the train how well I was able to see my gedit window (grey background, white letters) without the black shader on even when it was sunny outside, mainly because the seat right in front of me was some shade of grey.
So TLDR; it’s not great with bright sunlight, but depending on what you’re doing you might be able to adapt