My answers were the same for every case except the dancers; in that case, instead of saying I would both tip them and stop to comment, I said I would tip them but not stop to comment. The reason is that, in my experience, troupes of street dancers are more tightly focused on their work and not inclined to stop in between numbers to chat; they spend the time in between numbers sorting out with each other what they're going to do next, or just resting and grabbing a drink of water, since their work is more physical than most of the other types of artists you mention. Street musicians or chalk artists, in my experience, generally welcome compliments on their work; dancers seem to prefer to be left alone.