The MASTER controls volume but also starts to overdrive & compress just like an old amp would when turned up. Use this for a chimey/tweedy punch.
The PRE adds a gritty low-mid focused drive while still being highly reactive to your guitar's pickups and your picking attack. Use this for "tweed at 12" or "plexiglass at 11" type drive.
The SUSTAIN control introduces hard-clipping MOSFETs which results in a more modern + compressed distortion, taking you to 80s/90s style drive.
The deluxe allows for switching between two values of sustain, providing a drive + volume boost without a large impact to tone.
The Heroine was a happy accident. While playing around with ideas for standard drives, the thought came about formatting a pedal with two internal circuits for an amp-like approach to overdrive - having a "preamp" running into a relatively "master" side which clips only when hit hard by the pre, allowing you to control the amount of drive by how hard you attack, or by having the pre/sustain turned higher.