[PeterisP]

> I don't know how to create a class file, or a template (if that is a LaTeX thing). And since I've never seen anyone else do this, I guess that most academics don't either.

Exactly, academics usually don't do that - they write the text with appropriate markup, and then put it in the publisher's template and the formatting according to the appropriate standards is done. You can write your own template, but usually you use someone else's, with the big benefit that you can generally move your content to a very different template of a different publisher with minimal or no changes to your actual writing.

Now how would I do that in quarto - what (and how much) would I need to write to ensure that, for example, the captions for all the images and all the references to the images are all formatted in a specific manner? Because for quarto I would need to make my own template specifying the exact formatting and layout, and a quick browse of its documentation didn't lead me to any examples on how I would control that.

In sane environments there is a split between text and formatting, however, the formatting part has to be sufficiently powerful to meet the various requirements, so there is a certain quite high minimum bar to meet there. Latex works because I can rely that I will be able to easily get my markup laid out exactly as required by arbitrary standards, for any markdown-type standards I need some assurance that this will be possible and easy, that I won't need to (for example) go over all my references and do something to them.