I've always used AI as an editor, which is to say I give it the my efforts and ask it to highlight mistakes. They invariably find a few. They occasionally miss a few too, so they aren't particularly reliable editors.

They aren't reliable at anything I guess, but for English I have nothing else, and they are better than nothing. I do wish they would use a more effective way of highlighting their suggested changes, such as italics for new text and strikeout for deleted text.

Unless you are paid by the word, I struggling to think of why you would use an AI to create new text. The facts will be wrong, the tone won't be yours. "If I had more time, this would be shorter" is a truism here - AI can spit out an enormous amount of text in a very short time, text could be cut down to a fraction of the size with a bit of effort.