Cooling Fan Questions

My next PC will be built around an Asus Rampage Formula motherboard which I believe to be one of the best for overclocking. The CPU will be cooled by either a Thermalright IFX-14 or a Noctua NH-U12 cooler with 2 x 120mm fans, one each side (one pushing, one pulling).

My questions are:-

1. Is it possible to plug both fans into the cpu header so that they rotate at the same speed and can be controlled via SpeedFan?

2. What are the arguments for and against PWM (Pulse Width Modulation) when compared to voltage fan speed control?

3. Which fans should I get? (Must be quiet)

Thanks in advance