How big are style 19s? If it's 19inch that's big problem. These cars don't like a huge wheel.
You can safely lower the car. I say Eibach is best.
The rest of the information you seek like control arms etc. is already in this board and on bmwe34.net
If/when you do the shocks, the strut collar nut has to be torqed properly and it requries a dealer tool to get enough torque on it, strut should go to the dealer and have them press the shock in. 1/2 hr labor.