We have 3 Windows Phone devices, in addition to an iOS, Android and Kindle Fire devices. And it is more convenient to control the Google Chromecast from the phone.
Unlike the iOS (iPhone), Android and Kindle tablets, which allow me to watch Youtube videos and other content on the TV using Chromecast, there is no official support of the Chromecast on Windows Phone devices. So our Windows 8.1 phones were not useful when it came to Chromecast. Plus the Youtube app from the Windows Store is merely a wrapper around the mobile version of the Youtube web site. Poor navigation and video quality is the result.
Then I discovered Tubecast. TubeCast is an app that is available in Windows Store and not only has much better interface and video quality that the aforementioned "official" Youtube app, it lets you cast videos to ChromeCast too! The app version I got was free and the first 20 casts were free too. Then I had to pay a couple of bucks. Nice.
The only issue for me now is when I got a Chromecast for my mother and went to install it, I didn't bring any devices other than my (and her) WP. Plus she has a Windows 8.1 computer. The problem is during initial installation, the phone complained that Chrome browser was needed and the computer installed the Chromecast app and then indicated that WiFi connection was needed. The computer in question uses Ethernet wired connection to the WiFi router. So I will need to bring either an iOS or Android device to complete the setup.
Otherwise, WP 8.1 can now be used to control the Youtube playback on Chromecast. Nice.