The cpu PLL voltage on this chipset should be on auto. You should have no problems hitting a good overclock without messing with this.
Now, if you want to get a very high FSB (no magic number,.. just overclock as normal to get where you want) and are getting close to stable, but not quite,... then yes you might want to try bumping it up a little at a time to see if you can get that stable,.... I have heard that going over 2.0 on this setting can sometimes damage the processor,... so use cautiously I would say.
The DRAM skew, I am not quite as familiar with, however looking at it, I would say definitely leave on auto when clocking higher, especially with tighter ram settings as it looks like it could really create a mess in the RAM if one doesn't fully understand the interations of other ram timings, overclocked ram and skewing in conjunction (This is just my opinion on what it looks like it does though)