Would it be a good idea to use different "layouts" in an app?

Hey tscholze - I think it's 100% fine to use multiple patterns if the UX requires it. Sometimes this isn't necessary - Microsoft Teams is almost exclusively a "list detail" style app, and Excel is mostly "extended canvas" - but PowerPoint is a bit of a mix of "list detail" with "companion pane" elements. 

I tend to think of each view like it's a responsive web page - how should it look on a regular phone, on a foldable device, and on a tablet - and then think of how the elements should move/change/resize and pick the pattern that best matches.

One of your examples is a good one: settings views would almost always make sense as "list detail", no matter what UX/design pattern is best for the main app function.