i'd say klance and sheith are just about tied for popularity, if the fucking ship wars are any indication, but i can't think of a pairing for shiro that's anywhere near as popular as sheith, so like was said above, for any rando keith tagging out on a ship-flavored meme, any shiro they find is way way more likely to be down for the ship than not, which makes op's stubborn insistence on not stating their preferences that much more stupid.