They take epub files from publishers, but I believe what you buy from them still gets a kindle wrapper.

Good to know. So, if you get a DRM-free book on amazon, you can download it as epub?

Also, I wonder if longer code snippets are still wrapped around or are they introducing horizontal scrollbars? (for those who read on Kindle devices, web/mobile app, etc)

You can download it in Amazon‘s format, which (for DRM-free books) converts well to ePub in Calibe.

I think at this point the difference between AZW and ePub is even mostly in the container format.

Did Amazon change their DRM so it's harder to remove? I didn't have any issues with using calibre to remove the DRM from the e-books I bought on Amazon when I backed them up.