I have some files in WriteNow and WordPerfect format. The WriteNow files go back as far as 1987 and the WordPerfect files are from 1998 - 2001. Some I can read, others I can't open at all. Those I can read lose most of the formatting.
I'm talking basic "RTF-like" formatting for the most part, not super obscure proprietary word processing features à la the Home Depot that is MS Word. There are also some embedded graphics in whatever was the generic standard for Macintosh back then.
Even if a file might be in RTF, that standard has changed significantly over the years and formatting is lost for the most part.
I don't have the original software or a machine to run it on.