UWP is definitely overkill if you go through the trouble of writing all the MVVM bindings as I mentioned. But, for really quick things, I can type XAML faster than I can try to align gui elements with a mouse. Then you get the same code-behind file to do your heavy lifting. The WYSIWYG editor is far worse though, I pretty much would only use it for a preview and only touch the layout via the XAML.
Disagree. As someone who has worked extensively with both WPF and WinForms, they're just different programming paradigms (XAML vs Forms Designer), but once you get up to speed on WPF, you can develop interfaces, even "quick and dirty" ones, just as fast if not faster than WinForms. What exactly about WPF is overkill?
Yes, in that it has been replaced by WPF and now UWP. That said, it is complete, stable, and mature. You know what you're getting with it. Going by what Microsoft recommends (e.g. whatever the latest they've put out is) isn't always a good idea. For example, early on the WPF days, there were loads of bugs in the framework. Even today, with WPF not being actively developed, it's filled with quirks and bugs that you just come to know about by working with it a lot. I'm sure UWP is in a similar state right now to early WPF, which is why I'll avoid it until it becomes more proven.