In a bout of unintentional timing, Dave Leedy posted an episode of NotesIn9 I recorded about custom renderers. This should pair nicely with my last post - the video provides an explanation for what renderers are, how to attach them to your components, and an example of a basic renderer for a widget container. So if you're interested in going down that path (which you should be!), perhaps the video will help.

In it, I recommend looking at the source of Bootstrap4XPages, which remains an excellent source, and now my own renderers may prove useful as well. Once you have a good handle on how they work, the layout renderer may be a good resource.