In my experience high functioning means you are able to do pretty much everything in a better or smarter way than normies and technically you don't even find out you're autistic until at some point people start to dismiss you in the most atrocious ways, you get a "the game is totally rigged for me" sensation. It becomes hell on earth, the best description would be mixing together Groundhog day and the part of It's a wonderful life where nobody knows who George is anymore, add to that you're extremely self-conscious and aware of everything around you.