It's similar for cars, for example. You have a lot of engine configurations, such as V6, having inherent 1st order imbalance, but in most cases, for example, most 60-degree V6s, you just live with it because hydraulic engine mount and other normal dampening mechanism does the job well. However, for I4 with inherent 2nd order imbalance, usually you would need counter-rotating twin balancer shafts to help cancel the vibration, although the absolute amount of NVH is actually weaker. That's all because of the higher frequency nature of this 2nd order thing.
Like you have no idea what marine diesels are.
Talk about V8s, V10s, V12s, I8s, I12s even I16s.
16 Pielstick PA6 should be a 16 cylinder engine, a V-16, eight cylinders in one bank, another eight in the other.