I never give boone or any companion a different gun other than what they start with just cause I don't wanna have to feed them ammo, I have a habit of forgetting to do that and then they run out at a crucial moment, but I find that with his standard hunting rifle he still kills everything without a problem before I even knew they were in the general vicinity (and I have an 8 perception so they should show on my compass), but he's not gamebreaking as I can just choose not to take him with me, or I can just send him to the lucky 38 and leave him there to enjoy the room service.
Oh, I agree companions are like that. But they all are.
If you could use console commands you'd discover that every time you access companion inventory, any stat items they're wearing become 'stacked'. That is, if their armor gives them +2 to guns, eventually their guns skill is in the stratosphere. So Boone ends up with 200+ critchance etc. So take off the hat/item, it resets. Don't give it back, he never has more than 10-12critchance. He's not any more special vs. the other companions, that's all.
on topic:
Is anyone else curious who voted yes to gamebreakers after starting a new character, I see they voted yes but what gamebreakers did they come across.
Yes, I'd be curious to that as well.