Stack Overflow is for concrete problems; if it's somehow not working as intended.
Code Review is for code that works as intended, but could use improvements - to performance, to maintainability, or other goals.
Software Engineering is for the conceptual questions.
(I recall there's a diagram about that, but have been unable to find it back).
Since you have actual snippets, I'd say it's Stack Overflow for the things that are broken and Code Review for the things that need improvement.
Note that you don't have to do this "in parallel". You may ask Stack Overflow to help fix things first. And after that, post the larger, fixed codebase to Code Review.
I don't think Software Engineering is where you want to go, unless you want to re-consider the entire design.
