One other thing is, is it better to have more ram with clocked down speeds of 100 or to have less rams with all clocked properly at 133?
that depends on whether u need the additional memory or not. if u do things that require a lot of memory (such as a lot of multitasking, photo editing, etc), u'd be better off leaving the extra ram in and running at the slower speed, or ur system will start using virtual memory, which would be much slower than if u had the ram in there.
if u don't need so much memory, and ur mobo supports pc133, then feel free to use only the pc133 sticks, which would improve memory transfer rates. 256mb of ram is enough for most users, so this could be a viable option for u. however, if ur mobo only supports up to pc100, u should just leave all the ram in.
as for fooling around in the bios, remember that ur settings can only be as aggressive as ur weakest stick. if u have quality ram, u can try setting the CAS latency to 2 (down from 3; usually under "advanced chipset features"), which would provide a significant performance boost. also, ur pc133 ram has a better chance of handling CAS 2 at pc100 speeds than ur "real" pc100 sticks do, so this would be another possible reason to leave out the pc100 sticks.