Bender - yes with the P4S333-m you can adjust FSB one MHZ at a time. You can set the FSB/PCI ratio 100:33, then a bunch of intermediate settings such as 101:34 on up to 133:33 and you can set the FSB/mem ratio as 1:1, 4:3, 3:4 or 4:5.
I use the 133:33 setting for FSB/PCI and the 4:5 setting for FSB/mem at the 133FSB speed. So I am running 133FSB, 166mem, and 33 PCI bus.
You can also set the DDR properties. (Cas latency etc)
You can't change any voltages through BIOS.
Hope that helps in your decision!