The idea that "speaking mysteries" could be positive is contrary to the whole argument of the passage, which maintains speaking in church is to be for the purpose of communicating intelligently for the benefit of everyone. Chapter 12 shows that the gifts of the Spirit are given for the common good, not for personal benefit. Also, chapter 13, the qualities of love are not self-seeking.
On divers kinds of tongues, 1 Cor. 12:10, it is explained by 14:10, "There are, it may be, so many kinds of voices in the world, and none of them is without signification." These refer to the various languages which are spoken. All of them have meaning. The point is that none are spoken as meaningless gibberish.