Never fished that one, but have fished some of its neighbors. There’s some wild Trout in the South Mountain/Michaux SF area, but I have never fished a stream I would call “good” in that area. A lot of just “ok” streams, and IMO the best ones are the obvious ones…Mountain/Conococheague/Antietam/etc. There aren’t really any hidden gems in that area.
Kings Gap probably has fish, but it will be tiny. Just a couple square mile drainage. Probably a good one to try out when everything else bigger is blown out high. Otherwise, you’re not gonna have much water to work with.