This post, despite some mangling by Google Translate, is worth a see. It answers some — but not all — questions that have been asked here about the relationship between a tablet screen, video resolution, and the target TV screen. It’s also interesting that the dongle does DLNA (I’m not sure they all do).
It should be remembered that Miracast sends a compressed stream to the target device. This tends to introduce latency that can be frustrating if you plan to do any work with a mouse or other pointer. But for just seeing things on a large screen — video, photos, web pages — it’s good enough for right now. Of course, there’s always room for improvement. But this is still better than snaking a 10-20 foot HDMI cable from a tablet to a distant TV (when HDMI-out is available — something that’s not on the iFive Mini 3).