This is entirely theory, but I think it's a good one.
Given a fixed displacement, say, 2.0L, we have 3 engines. First is an I-4. Second is a V-8. Third is a W-12 (for compactness).
I theorize that the V-8 will produce more usable torque at lower RPM's than the I-4, and the W-12 will likewise "lower" the bar over the V-8.
I imagine a small displacement V-12 spinning at 1,100-1,200 RPM, or even less, on the highway.
It's giving me thoughts about building an engine from scratch.
My theory comes from reading the charts in the following page:
Torsional Characteristics of Piston Engine Output, by EPI Inc.