Hello pmichalski, and welcome to the forum.
You’ve asked an excellent question about why Scrivener offers so many section types and how someone might use them effectively. The forum has some discussions on this topic, like this one or this one. Reviewing them might be helpful for you.
It also might be helpful to think of the documents in your project in terms of groups. Those groups will be based on having documents at one level of your project sharing formatting, while documents at a different level will have their own formatting.
In this screenshot, I’ve marked my Part 1 folder with a yellow arrow. Let’s say that I want Scrivener to compile every folder at this level of my outline so that the folder’s title becomes a heading that is centered on the page. But, I do not want any text from that folder. I would assign all folders at this level of my project with the same section type. That would allow me to just get their titles as headings.
The folder marked with a blue arrow would get a different section type so I could turn it and all other folders at that level into chapter headings. In the “Why This Topic” folder, I actually have text written, which I might or might not want to include in my output file.
Items at the red arrow level would have a different section type so I can get their titles as section headings and their text in the output file. If I wanted headings from their subordinate documents, I could have those subordinate documents use the same section type. Or, I could use a different one if I only wanted the text but not the titles.
I could continue adding new section types as needed to get the headings/text in the output file the way I’d like. And, on the main compile page, you’ll see when you click into the “Assign Section Layouts” area that you can assign a different example text to each section type you’re using. That example text demonstrates how all the documents at that level might look in the output file.
Those section types can also be customized so that you can change the size of the headings for each group of documents, include or exclude notes or synopses, and so on.
Does that information help you to see how the section types are being used?