I float back and forth between most of these options. MacWrite Pro, for its compactness and speed on even very slow machines, ClarisWorks/AppleWorks 4 and 5 for their completeness, and Office/Word 98 for familiarity and file compatibility.
WordPerfect 3.5 is also good, and, Nisus Writer is also fairly good.
I'd say it depends on how in-depth you really want to go. MacWrite Pro and ClarisWorks are "easy" but constructing complicated documents with lots of different formatting requires a little bit more of a learning curve than on Word 98, which uses styling in almost the exact same way you'll be used to as any version of Word from 1997 forward.
(The concept is roughly the same on both sides, but Word exposes the controls for it in what I'd consider to be a more clear way, and Apple's way of exposing styling would/could have the side-effect of encouraging people to do manual formatting rather than declaring styling.)
There's a handful of good books at
Vintage Apple (vintageapple.org) and a good one to look at should be "The Mac is not a Typewriter" by Robin Williams. Both versions (1990 and 1996) are on this site. That book talks a lot about the concepts of word processing and although I don't know if the term "semantic styling" is used, shows the power of setting and using styles, as opposed to manually formatting things. (Disclaimer: I've skimmed but not done a detailed read-through of these books)
It kind of depends on what your goal is, and, the effort it takes to set styles (especially in things other than Word, maybe WordPerfect) is definitely worth it for when you need to produce a lot of consistent documents (possibly with the help of a template), or when you need to product large documents with things like multiple sections.
Depending on the scenario, too, you can use HTML editing applications to do writing and open the HTML files in a browser or a newer HTML authoring tool on your modern computer, although most of those won't have, like, editing tools like spelling or grammar checking.