You have to give your dog positive, constructive outlets for all that prey drive.
As others have said, tug is a great game to channel all that drive into constructive activities. Play fetch until her tongue hangs to the ground, and up your leadership through formal obedience training, structured play activities, and NILF. Once she is secure with the knowledge that you are a strong pack leader, you checking out what she alerting to and saying enough should be enough to convince her that her job is done.
One thing you can try, is when she does alert you, and you check it out, praise her for the alert. If she continues to bark and go nuts, send her to a spot and make her stay there until you release her.
The ongoing barking at people and noises is because she feels that the whole responsibility of keeping the property safe is on her shoulders, and she feels overwhelmed by it, and puts on a great big show to scare the potential threat away. She needs to know that you can step up and take control, so act in a matter that communicates this to her. I'm not sure exactly how to achieve this, some people have it naturally, others have to work at it, but the end result is the same.
As for chasing light reflections, does this come from laser play? Very addictive behaviour that can turn into serious OCD - stop all games where she is chasing light and/or shadows, and stop and redirect and such behaviour. You'll have to watch her and be on top of this and be very consistent in absolutely not allowing her to chase lights and shadows - redirect her need to chase light to playing tug with you - make other activities more fun and rewarding - play lots with her, so she looks to you to satisfy her prey drive, not kids, strangers, or moving light flashes.
Gryffon Vom Wildhaus
BH, OB1, TR1, AD
Rottweiler/Hairy Dog mix?? 2004-2015