Section 5.5 Customizations
There are some aspects of your output that are entirely divorced from the actual content, and are presumably all about how that content is presented. Two good examples are the size of the font used in LaTeX/PDF/print output, and the granularity of web pages in HTML output (by this we mean, is each web page a whole chapter, a whole section, a whole subsection?). Producing output with varying values of these parameters does absolutely nothing to change your content in any way, and so should not be a part of your writing, nor a concern while you concentrating on your writing.
Therefore, many aspects of how your writing is presented is accomplished by your publisher. Note that this is very different from your role as the author of your project. When your project is mature then you can consult with your publisher about how to best present your project to your audience. An entire part of this guide is devoted to this process (Part IV), but if you are curious, the first part of Chapter 26 can serve as an introduction.