G1.Sniper M3 fan questions/issues

I just finished up my new build but am having a hard time getting the fans to work as desired. I have 3 pwm fans running off the system headers and am using a splitter w/molex off the cpu header to run the 2 cooler fans.

Problem 1: From what I can tell from the manual and the bios, the 3 system fans are grouped together. The problem is that fan 3 runs about 300 rpm faster than the other 2 (700-750 vs 1000). They do all respond to increases and decreases in ET6. Fans 1 and 2 are intakes and fan 3 is the only exhaust. They are all 120mm Cougar pwm fans. Any idea what's going on?

Problem 2: I can't figure out how to use the voltage settings to quiet the cpu cooler fans. I've set the bios CPU Fan Control setting to voltage and normal as is directed in the manual. I don't know where to set the desired voltage though. I can't find any settings in ET6 or Speedfan. They are 3 pin Noctua Nf-12p and are running at 1300rpm.

Appreciate the help.

If it helps, the case is a Silverstone PS07.