> So how well is a static site generator suited for this? Do I want to build thousands of pages every time I start the site locally?
Take a look at Astro[1]. Astro comes with a development server and it will not build a thing unless you want it to.
Also, in contrast to classic static site generators Astro relies on components instead of templates which reduces cognitive complexity dramatically (to me anyway).
[1]: https://astro.build/