Extra holes - Definitely.
Saddlebag supprt rails - Definitely.
Drags come in Classic and Custom versions.
Biggest difference on the Classics are the long sweeping metal mudguards. Other details: the forks have chunky shrouds over them so they look beefier, the front wheel is wider, the seat is fatter and more contoured, the bars are more M shaped and the battery/compartment covers are usually the same colour as the tank.
Custom version (the best) is less stylised, and slightly more minimalistic. The covers are chromed, the mudguards are shorter and made of plastic (as a result, the Custom is 20kg lighter) and a few more minor details.
The Classic:
The Custom:
Hope that helps.
I'm a 650 Drag nut, as are many here, so feel free to ask any questions!