This is a good question. A few years ago when I was stupidly throwing my 7" AC Plug on 16lb I had it snap off on the cast 3 times (got it back every time too). 16lb is just way to light for these plugs. As far as breaking fish off, I have broken off one fish. I was using 20lb and had just tied the plug on. When I cinched the knot the line slipped a tiny bit. I was in a hurry and like a fool did not re-tie. A few casts later a 4 pounder ate my plug with not more than 6 or 7 feet of line out. Pow see ya later. I blame that one on the knot but the fish bashing it so close to the boat probably contributed also.
Now with the 9 and 12 inch plugs I use only 25 and 30lb test. I was fishing 30 at Clear. It's a little springy on a small reel but a Corsair 300 holds it ok. There is just no reason in hell to use lighter line especially in a lake like Clear Lake.
My 15 pounder I caught on 25lb Triple Fish. The fish dind't put up that much of a fight but I was still glad I had the right tackle including the line and the 9 foot rod. It allowed me to steer the fish out of the trees and into open water very easily.