Book design - really just the interior parts for now. I have a (private) website for writing branching fiction (kinda like CYOA but not in second-person present

Book design - really just the interior parts for now. I have a (private) website for writing branching fiction (kinda like CYOA but not in second-person present tense), and my friends and I have been using it to write a novel over the last year or so. So far it's about 250 chapters out of a projected 350, it should end up just under 1000 pages so I'll probably have to break it into two volumes. Ideally I'd like to press a button on the site and have it generate a manuscript - so far I've been looking at a combination of markdown, pandoc, and LaTeX for the formatted form. From what I understand that's frowned upon for Real Publishers, but works well for the DIY process (amazon, book baby, Ingram). I'm playing around with LaTeX templates now, and have a subsection of the book laid out manually now, using various guidelines I can find for font, font size, margins, etc. I'm also writing a separate book more having to do with how people can respectfully share reasoned conclusions with each other - for that, I'm also using a LaTeX book template and am just writing it in LaTeX, since it's kind of fun to see an approximation of what the actual book would look like as I write it. There's a long way to go on learning this though and I haven't found a lot of good resources, so I'm definitely open to suggestions for folks who have written good technical dynamic pipelines for book publishing - particularly anything that can be wired into a web backend that starts with markdown data.