Must admit I'm getting lost off by all these titles as well!
I always thought a director of football would be the one who would identify targets (heading up the recruitment team) who would suit the style of play the club was implementing. There'd be discussion with the head coach but by and large positions would be identified and they'd get the players.
Technical director was more about the coaching and staffing side of things, especially in terms of recruiting and developing staff.
For me, a sporting director sounds like someone who would sort of have a role in both of those. In a large enough club you might have a DoF, an academy manager/ director and a technical director who report to the sporting director. But if that's the case I don't see the need for a chairman. But if this lad is coming in as the sporting director type role then I don't see how we could also have someone above him. Time will tell I suppose