Previously buried in the Axe-Fx II forum section, and now introduced here:
Yek's Guide to the Fractal Audio Drive Models
The guide (PDF) describes all Drive types in depth.
Note: Fractal Audio's modeling of drives has been improved in firmware Ares 3.02 and later for the Axe-Fx III, changing gain, output level, characteristics and tone. Tips and information for the current firmware for the Axe-Fx III may not apply to the Drive types in earlier firmware, including the AX8, FX8 and Axe-Fx II. Therefore, the guide for older firmware is still available separately.
View attachment 71902