Will NPC ships reap any benefit from these new improvements and maybe become more deadly?

They take advantage of it as players do. It's purely down to AI behaviors. I wouldn't say they're any worse than before.

Actually, 3.10 has a couple of IFCS bug fixes that make them not cheat anymore. Surprise. There was a bug that when an AI ship pulled up, the acceleration and the rotation were way bigger than they used to be, and so certain ships could instantly turn around, and now they're actually limited to what they're actually capable of. That streamlines the whole experience. In terms of weapons, I think AI ships do not use fixed assist; that's for players only.