I was a bit surprised the article didn't mention Windows on ARM at all. Following the Apple announcement, I managed to snag a Windows laptop that uses the Qualcomm Snapdragon 850 ARM SoC for dramatically less than MSRP on eBay. (To be fair, they were selling it for parts since they couldn't figure out how to remove the password. Wiping the drive and reinstalling Windows was easy enough.) For the most part, it feels just like Windows. Every app I've downloaded has _just worked_. That being said, there's definitely at least one app that won't (Wireguard since it requires an ARM64 driver to work). I've actually been tracking which software provides an ARM64 version[1]. Sadly, it looks like virtually every toolchain still needs to update to support ARM64 on Windows. I'm tracking a handful of GitHub issues, and support is definitely in the pipeline, but it's slow going. For example, .NET _still_ doesn't support Windows on ARM, despite the fact it's the flagship way to build apps on Windows, and ARM64 Windows devices have been available for almost two years.
Is plain win32 API supported on arm64/Windows? Is there a version of MSVC? Or does one use mingw?
Win32 is supported with MSVC just fine.
You can also use MinGW with LLVM (not MinGW with GCC), available at: https://github.com/mstorsjo/llvm-mingw