Modest, hands down. Noivern is already pretty freaking fast, but if you still want it to have even better speed, just throw in some speed EVs. Also, make sure it has Infiltrator, that’s one of the things that really makes it hated by the opponent. When you hatch it and evolve it, it can learn BoomBurst, Dragon Pulse, and Hurricane as egg moves, and then you can use a TM for Roost, which is my suggested moveset. Yeah, I know you can go with Draco Meteor, but then there’s that Special Attack drop, and every other move you have is special, unless you have a Pokémon you an switch out to that can take a hit, which then it’s okay to have Draco Meteor.
And on top of everything, it’s best for Noivern to be an all-out attacker, since it doesn’t have very good buffing moves that it can learn. I have mine hold the leftvovers, but the Choice Specs are also a good choice, again if if you have a Pokémon that can take a hit, because if you spam BoomBurst, and you run out of PP, or you face a ghost-type, you’re pretty much screwed.