Jonathan,
Per CFR 27, Bourbon does not allow the addition of enzymes , so only the natural ones' in the grains may be used. You can still use the enzymes, but if you do you must call it something else.
The Alcohol Text Book, The Pracital Distiller and Whiskey all contain classical Bourbon formulae.
I have found that the commercial malts tastes like the company that made it as well as the genus and species. There are plenty of malts and grains yet to discovered for distilling. The reason the companies can't tell you is because they don't know.
Best regards,
Don