For example, "Hearts" or "It Can Happen".
I've heard Yes just wrote words that sound good to sing without worrying about meaning. Any truth?
That in fact seems to be the case, as stated by this one guy in this one video. He seems trustworthy, so we might as well go with what he says. For real tho, that's on their early records, their later seem to be more down-to-earth, specially 90125, in which Jon wrote very little stuff, and the rest of the writers relied more on the theme rather than the words, if that makes sense. That's just an hypothesis tho. As for what do they (the early ones) mean, I believe Jon was a very spiritual/loving kinda guy, so most of his lyrics reflect that, for instance, Close To The Edge has parts of his dreams, his ideals, "finding your higher self", metaphors, etc. Roundabout supposedly talks about a "psychedelic-country life"... Don't ask me.
If those specific examples you wish to know, then I know for sure that it was actually Chris Squire who wrote most of It Can Happen's lyrics. "That was a message of hope, and just making a way through the world looking for the good route - the one that suits you and leads on to better things.", he says. As for Hearts, actually written by Jon, it seems to be one of his "reciprocal love songs", as I like to call them. I'm not sure on his formula on this one, he probably gave classical poetry a try, or he probably stuck to his earlier formula.