The added delay from enabling RAW (the CHDK CRW kind) comes almost entirely from writing it to the SD card. Make sure you have a fast card. Shooting to DNG is somewhat slower than CHDK CRW, because there's some processing involved.
JPEG quality change does speed things up because file size becomes smaller, but when RAW is enabled this is not a big deal because the RAW is usually significantly larger than the JPEG, especially if you don't use the highest JPEG quality. If your SD card is fast, do not decrease JPEG resolution (only decrease quality to minimum) because scaling the image down takes more time than what you gain from the reduced file size.
If you require fast burst speeds, you just can't use RAW or DNG which is why CHDK offers this setting: "RAW Parameters" -> "RAW Exceptions Menu" -> "Disable RAW @ Burst".
