Well I am only able to offer some lame answers. Mostly because quality answers would take a very long time to construct. But here you go

• This really depends on what your building. Maybe find a n established project that's similar to yours and mimick its structure. There are many patterns available.
• Google it, try it, repeat. Python is loaded with "syntactic sugar". That leaves you with lots of options for how to structure and format your code. Which leads to many varying opinions. This is extra noteworthy for larger dev teams because of varying experience levels. You might be able to write a short, clear but of code that some devs won't understand. Lots of good options leads to a lack of clear choices. Opinions will vary.
• Again, lots of options. I like using the Black formatter because it gives you very few options and forces you into some style choices. Even the ones I don't like 🙂
• Oh boy. Google it. Extensively. Google it for several hours and then read some source code. Do this every time you start a new project 😂.
• I don't have a specific tutorial unfortunately. But the idea is that your "pyenv" directory will contain the packages your project depends on. Maybe the python installation too. And every one of these items will be a specific version. Because this is all installed in a single directory for each project, you can easily have different projects use and rely on different versions of the same dependency. This avoids all sorts of problems where you accidentally build and test locally using the wrong package version. I think a common practice is to create the "env" folder in the root of your git repo. And add "env/" to your gut ignore. Don't trust that exact syntax btw 😅