Editors such as those are designed to process files using a word processor format, not plain text.
If you want to see all the file types that a program can process then try creating a file using it. The editors you specify will each offer a large list of possibilities, except not Notepad.
As in your question about counting letters in the New Testament, you need to be specific. Either you mean plain text or formatted text. RTF text is different from HTML text and there are many other formats. With plain text the data could be ASCII or it could be one of many possible ways to use Unicode.
My other question doesn’t have anything to do with this question and I was specific — a file type that all of the aforementioned program types could process or let the user edit, at least to some degree (depending on the program type).