The overall speed of Stutter is controlled by the WPM rate. Most users will find this number comfortable in the 600-800 range after a few minutes of practice. Speeds of up to 1200 can be achieved with regular practice.
When beginning to Stutter, the Slow Start Count will ease you in by slowly ramping up to full speed over this many words.
The Delay settings are speed multipliers. If a word normally were to display for one second, a multiplier of 1.5 would make that 1.5 seconds. The defaults are designed to feel natural.