Three'd. I do recall that being the pinnacle of word-processor efficiency for me. 5 was when the Windows-UI started invading, it became massively slower, and wouldn't run off a floppy, thus couldn't be used in my school's Mac lab.
After I got out of school, I switched to BBEdit, and Pagemaker if I needed formatting. And now vim is my world. Libreoffice gets to annoy me if I need paginated formatting, but that happens less and less.
More or less my experience: Word 4 was snappy on my SE/30, had all the features you ever needed, and then some, and the interface didn't get in the way of anything.
Now 95% of my tube time is in Emacs, and most things are written in LaTeX. Though occasionally I still need Word, and I've been happy with Office for Mac (2016?) so far. (I really want to like LibreOffice, but...)