A shooting head is really an extreme weight forward line, where the running line is separate to the fly line, knotted to the end of the head, and made from a thinner and lighter material like mono, braid, or a bespoke very light fly line. In that respect it differs from the running line on a standard WF line.
Having been popular back in the day of Geoff Bucknall and Dick Walker, shooting heads for trout fishing are now seen by most anglers as a very specialist tool, as BB says, for long range and / or deep fishing on reservoirs. The achilles heel is always the backing. Mono tangles dreadfully unless really carefully managed, and should be frequently replaced because once it's been tangled it's never as good again; braid is abrasive so it cuts your fingers and being semi-buoyant it plays havoc with sinking times that need to be carefully managed; and bespoke fly line backing like Airflo Polyshoot is good to use but you lose a bit of distance.
Given all of this....can't see what a shooting head system will buy you for relatively casual use