Some boys can be nesty or beaky, but they're the minority. None of my four boys are nesty or very beaky, though Termite is the most likely to pinch if he's cranky and his authority is not respected! For the most part, they're very spirited yet cuddly and loving. They'll boss you, but you'll be smiling.
As for conures - depending on the type, they can be bitey. GCCs most of all so far, but I think the Jekyll/Hyde thing may apply to others as well (my ex had a dusky conure that would love on you briefly and then bite the tar out of you without apparent warning or provocation). I think lovies are more obvious and don't bite as often or as hard:
"I want, you deny - I'm upset!"
"You're in my way!"
"Stop that annoying thing right now!"
"This is mine, too, and I don't want to share right now!"
"Why are you putting me back already?!"