While sectional titles aren't as stylistically free as the chapter page, it is still important to carry over the style of the chapter page to sections, subsections and other such entries you have throughout your text. Thus, if the chapter style contained sans-serif text and a line below the text, it might be relevant to make the sections be sans-serif and possibly with both a line on top and below the section title.
While memoir is indeed very configurable, it doesn't contain quite as an elaborate amount of commands to configure the sections, subsections and so forth. The primary command to customise with here is the
\setXheadstyle where X can be sec, subsec, or subsubsec (and possibly more). So writing up the section style mentioned above would look like this:
Here we set the style to our custom command that will be called with the section number and title as an argument. This gives us the following output when compiled:
Since styling in this way is fairly simple, I will not go into painstriking detail of how to create more section styles. It is, though, useful to note that there are three more useful commands to know of:
\setXindent. The two first commands take lengths such as ‘-3.5ex plus -1ex minus -.2ex’ as arguments, and the last command just takes a regular length as an argument.
To see how these lengths can be used in practice, please refer to the memoir manual.