In my experience, the disk cache is usually faster that the USB, even if the USB is 2.0. Forcing windows to use the readyboost on a USB drive when you have enough ram may even hinder your performance, unless the drive is an old 5400 super slow read/write drive
Also disabling the pagefile is not the best idea, setting it static is the best. Some apps require one.
If you disable the pagefile and Windows needs somewhere to page the data, it will page it it to kernel, which is not the best idea. If you have it too low, windows will dynamically make it bigger, hindering performance as well.
I have 6GB of RAM, I still set my pagefile to 6GB static, with out any readyboost drives, my drive's cache is faster than querying the USB drive over USB.
I recommend turning off the Windows write-cache buffer if you want more performance from your drives, but be sure that you have a power backup in case of loss of power. Not buffering the write cache could lead to loss of data if you lose power in midst of a write.
Computer Management> Device Manager>Disk Drives>[Select one]>Properties>Policies>Enable write cache>Turn Off write-cache buffer
Depending on your drive type, you may have even more performance options.