Defensive shotgunning is sighted fire and requires a solid stock and decent sights. I have never seen a gun with a folding stock at any school or recommended by any trainer.
Buckshot is reported to be more effective at close range, which is the shotgun's purvue. In training, one does a "slug select" for longer range shots. Longer range means the range at which your gun will no longer keep your buckshot load entirely on the target. That can vary considerably with guns and loads and targets.
The best investment you can make before buying and modifying a shotgun is to read "The Tactical Shotgun" by Gabe Suarez.
Buckshot is reported to be more effective at close range, which is the shotgun's purvue. In training, one does a "slug select" for longer range shots. Longer range means the range at which your gun will no longer keep your buckshot load entirely on the target. That can vary considerably with guns and loads and targets.
The best investment you can make before buying and modifying a shotgun is to read "The Tactical Shotgun" by Gabe Suarez.