城府 almost always appears with
深 (deep) —
城府很深 /
城府极深 — describing someone who hides their thoughts and plans behind a guarded exterior. Note the moral ambiguity: it is a sign of shrewdness or savvy, but also of being hard to trust. The opposite is
心直口快 (xīn zhí kǒu kuài, "straight heart, quick mouth").