The p5q's overvolt everything on auto. Just setting all relevant voltages to a couple notches past stock/auto is almost a necessity to have voltages in spec.
These boards are great OC's but they are finicky and have a couple quirks compared to the gigabyte's.
Yes, for any overclock you want...
What BIOS are you using? You might want to check out Ket's mBIOS for the p5q's, they have better memory support. General consensus says they are better for OC'n especially on quads.
The p5q's are hit n' miss with the straps, you're better off leaving them on auto and manually selecting the...