A lot is done by Scrivener for you, but loading your packags and settings is completely in your control. That’s the beauty of what Scrivener has done for you.
There are settings in the Text Layout Format settings in compile. I also have in the “Front Matter” a document holding my own set of package loads and settings.
I can only suggest you create a simple test document based on Scrivener’s LaTeX template, read the concise documentation, and give it a go. I use “texmaker” to compile the *.tex file created by Scrivener.
I do no writing in a LaTeX editor as some of the “cool kids” do, but I like to spend my time more productively writing in Scrivener. 