1- from what I've read/seen Aromatic malt is a specific type of malt, not a class of malts. It is kilned higher, so you wouldn't use it as a significant percentage of your grist like you would with Vienna or Munich.
2 - The more a malt is kilned, the less enzymes it contains. Generally, light malts like basic 2 row, British Pale Ale, and Pilsner malt have a lot of enzymes. They have enough to convert themselves, and the rest of the grist. Malts like Vienna or Munich only have enough to convert themsleves. That means if you have other character malts in the grist, you won't get good conversion. In addition, grains like unmalted wheat, corn and rice contain no enzymes. Neither do roasted grains like Chocolate and Roast Barley (at least not an appreciable amount)
Hope this helps.