Always consult the official Owners Manuals first
Yeks Guide to the Fractal Audio Drive Models
Forum member Yek (Alexander van Engelen) describes each Drive model in his Guide to the Fractal Audio Drive Models (PDF).
Current edition: August 2018.
The guide was preceded by a series of threads on Fractal Audio's user forum. Forum member Simviz assisted with migrating the contents of the threads to a PDF guide. Yek updates the PDF guide periodically.
Brief information about the Drive models, derived from the forum threads and PDF guide, is also available on this wiki page.
If you find the guide useful, consider donating to a good cause.
Yek created simple "Drive+Amp+Cab" presets to demonstrate most Drive models. Use FracTool to convert them if necessary.
Forum member Leon Todd (aka "2112") created an in-depth tutorial about tweaking each Drive model.