Scouting range is set by your club`s board and does not depend on your scouting staff. It`s more or less tied with club stature, bigger clubs have bigger scouting range.
I`ve understod that HoYD uses scouting knowledge as base of the ”pool of youth” intake is taken from. In your case having an French HoYD in an Italian club, would increase the possibility of getting a French youth in your club. HoYD also tends to find youths close to his own personality, so it`s beneficial to have a HoYD with professional, determined etc. personality.