According to some recent reddit threads, the Chromecast and Chromecast v2 supports 720p @60fps and 1080p @30fps, and, according to testing the Chromecast Ultra supports 1080p @60fps. Because of the possibility of foul language on reddit, which may violate the posting rules on gsmarena, I do not believe it is wise to link the threads here.
veryangrynerd, 24 Sep 2016120Hz video (60fps) Wut????Yes, makes no sense. May be confusing interlaced with progressive video.