Word 2000 (which is getting harder and harder to make work with every release of a new Windows, but has exactly the functionality I want, so I cling to it like surviving in a vast ocean on a raft that is being eaten away, bit by bit, by circling sharks). I save the files as .rtf, which takes up less space and places fewer weird characters in a file that have to be removed later, before publishing.
When I need a docx format or pdf, I re-save via LibreOffice; when I need an EPUB or something else, I use Calibre to convert the rtf file. Another option is Google docs. I'm not impressed with Scrivener, which seems to me like a good way to avoid really writing.
I just finished a new novel of 78K, which is pretty typical. I'll finish the year having written ~400,000 new words of fiction. Last year, I wrote 500,000. I also write 50,000 words of articles every year and too many words in answers here.