It's the sound of an exhalation of breath, yes. It can't really be a 'yell' or a 'laugh', but a loud ふおっ could be sort of shout-like, it's often an 'oof' kind of sound, and it could also be a prelude to a laugh or a suppressed laugh. Most commonly it's basically a grunt of surprise or in response to being hit by something. It's got more tension to it than ふわぁ (and near relatives) which is more common for sigh-like exhalations.
