I haven't used windows in a long time, but on Android there's a dialog to pick browser and search engine on setup. So I'd assume that they're also bound by DMA in the same way.
No
Source? The only news I can find about is EU users can uninstall it.
There used to be a browser chooser app, but it was removed many years ago now. Now you can just uninstall edge instead.
They do. Good luck getting Firefox otherwise, so I don't mind it.
Similarly, they bundle Bing as the Web search in the start menu.