You can use MODBIN to snoop through the BIOS binary file and make modifications. I use it all the time to customize BIOS loads for my client's machines.
There are a number of BIOS features that various board makers choose to hide or make inoperable. These can be enabled using MODBIN4 or MODBIN6 for the newer BIOS.
Caveat: if you aren't at a level of comfort diddling in the BIOS, then leave it alone. If you screw up the Windows Registry, you can reinstall Windows. If you screw up the BIOS, things are worse.
As for aggressive memory timings, a DAW is not the place to be tinkering with overclocking, etc. Leave things box-stock, and they run better. Every ASUS board I've seen tested is usually right at the top of the benchmarks, even if they don't use aggressive memory timings.
Yes, the KT133 family has the pci burst speed bug and the USB issues. The USB issue can be circumvented by disabling the onboard controller and using a quality USB card. There are patches out there to hack the KT133 chipset for some of these problems, especially with SoundBlaster cards.