Yes, absolutely. You can follow the exact same steps as in the article; Just use Python 3.5 or 3.6 and omit the `buildvm` and `runvm` steps. The only limitations on Windows are that the app is not yet code signed and there are no automatic updates (yet).
Qt as an ecosystem is fairly complete for general application development. It includes, among other things, concurrency primitives (QtConcurrent) that are trivial to use*, sockets, database support, serial port drivers and charting (qwt for example). Plus lots of useful tidbits I keep finding like accessing standard system temp directories, making temporary files and adding registry keys (or equivalent).
I've never used GTK in anger, but presumably there's some feature overlap. At times I've used Qt without any GUI components because it's so convenient (nicer than Boost for sure).
It also leverages native GUI frameworks so most applications will blend in with the platform you're writing for (last time I tried GTK this wasn't the default). It's easy to style with CSS if you need it.
From the perspective of a Windows user, GTK+ 3 does a less-good job of fitting in than Qt Widgets 5. Even with the win32 theme (GTK seems to use the Adwaita theme by default) GTK is missing shadows and the icon gutter in menus, and animations on push buttons and scrollbars. Qt Widgets 5 (with the Windows style, not the Fusion style) gets those right, and as a result, Qt apps look much more like native apps.
GTK+3 fits well only into GNOME. If you want to make an app that works and behaves well under other DEs, Windows or macOS, then even GTK+2 would be a better choice. Basic stuff works, but as soon as you want to use something more platform specific, like notifications, event sounds, systray, platform native decorations etc. then GTK+3 is going to give you a hard time.
