Can't you just use Transmission on windows? It's a GTK app and they're better on Windows than MacOS. Or you can always use it's web interface on Windows.
Transmission on OS X uses native UI components[1] rather than GTK. In fact they seem to have 3 sets of UI code (AppKit, GTK+, Qt), plus the web interface, plus whatever they're using on Windows (might be GTK+ or Qt there?).
Having used Transmission on both Windows and OS X, I vastly prefer the OS X version. It never crashes, gives nice notifications, and is generally very pleasant to use.
[1] https://www.transmissionbt.com/images/screenshots/Mac-Large....