Head on battles, the Convergence would need all 200 of their ships. Maybe half to fight just one Nation. But their ships will have long intervals before any arrive. And the 200 may not even come to this galaxy. But 1 Hive has the ability to take a Nation on when it has landed on a planet and is fighting a Nation on the ground only. It can, not saying it is guaranteed, just increased chances.

The Convergence prefer co-existence, to learn from other races and adapt and evolve. They get a "good feeling" from actually evolving into something new or adding something new, so they like to observe other species and take their traits