“GM built a prototype Cadillac with a 1000 hp V16.”
I don’t see much point in a lot of cylinders except the more the smoother the engine. Eight big cylinders can give the same power as 12 or 16 smaller ones.
The Rolls Royce Merlin engine is a 12-cylinder V engine. I think the large number of smaller cylinders and shorter strokes gave a narrower engine which was needed for the aircraft it was used in.
The long crankshafts of v12 and v16 engines can have torsional flex that limits the torque imulses that can be applied by the pistons.
I am skeptical that a 12 cylinder engine is inherently capable of more power output than, say, an 8 cylinder.
Mostly it is the relation of the valve size to cylinder diameter.
Also, piston acceleration.
The rods tend to stretch and PULL apart.