Cylinders and firing order
Info in conjunction with your post is that balance in the engine is important but the dynamic balancer takes care of that problem.
The rods except the master rod are articulated, and because they are, the magneto cam is compensated to address that issue.
The magneto cam compensation is actually cut into the cam and is slightly differernt for each articulated rod so that they will fire at the correct time to give the engine the proper peak pressure point (2-10 degrees after top dead center) and power overlap to continue the "flywheel effect" in the engine.