How far should I take merging together different Pages on the same Topic?

Fairly new to SEO, and I have a very basic question. I hear a lot that you should try to move content together / group stuff, so that you do not have a lot of thin content on your site. However, I don't fully understand how far I should take this?

I get it that "Best Philosophy of Mind Books in 2021" should maybe be merged with "Best Philosophy of Science Books in 2021", in order to create a "Best Philosophy Books in 2021" and then have "Philosophy of mind" and "Philosophy of Science" as two subheadings on the page. That makes sense to me. But what if those topics are both already very long pieces of content? (4000 words +)?

Also, what about stuff like: "Best Books on Philosophy in 2021" and "Best Philosophy Articles of 2021" - those are very different topics in my opinion, and I'm not sure if searching for A means that you are also looking for B? I'm a bit confused about how far I should take this.

or for example: "Best Books to Learn Javascript for Beginners" and "Best Books to Learn Javascript for Intermediates"? - sure, those could be one giant blog post, but I'm not sure it makes a lot of sense? Or am I misunderstanding something.