The difference in writing style between a book chapter and article in a journal
You would want your chapter to fit into the whole project, whereas a journal article can usually stand alone.

Your chapter should not duplicate material in other chapters, although you may refer to material in another chapter.

You will want your chapter to be generally accessible.  For the specialized journal article, that doesn't matter so much.

The editor (could be more than one) may want to be rather more involved in choosing the content, organization, presentation, etc.,for a book project than for an isolated article.

To get a feel for the style desired, you could ask the editor(s) for one or more examples of the desired style.