I also have Plex and Channels. Plex is AWESOME for managing your movies and other media. The UI is beautiful, and I love the Netflix-like experience. But when it comes to DVR and live TV, my experience is that it is mediocre at best. It works. Sometimes. Often it doesn’t. And if you are using it to stream to Apple devices, it has to transcode which slows the time it takes to start watching a stream.
Channels, on the other hand, is AMAZING for DVR and live TV. I have used it on Apple TV, iPhone, and iPad, and they all work perfectly. Even remote streaming is great (assuming you have the bandwidth). The UI is great, and the video begins to play almost immediately.
You can schedule, change, and delete recordings remotely right through the app no matter where you are. You should be able to watch on any of the platforms you listed.
And lastly, you’ll find that Channels support is great. They respond to emails and community forum posts, generally within a few hours. If you need help from someone at Plex, don’t hold your breath!
Enjoy!