Breaking it down into regular English...
Size matters,.. bigger is more...
... but speed matters, too...
It's all about burning energy...
... a bigger chamber will hold more fuel to burn
(displacement)...
... faster refilling of the chamber, will burn more
(fast moving mufti-chambers = RPM)...
... squeezing more fuel into the chamber
(compression)...
... better flow, will move fuel faster
(air, carb, valves, exhaust,will add flow)...
... and, you need enough spark to light it...
Mufti-cylinder machines can make higher RPM's with less massive moving parts... and make more power...
... but,..the higher the the RPM goes, the narrower, and higher the power-band is located...
So,.. gaining HP by using mufti-cylinders, and better flow, raise HP at the expense of torque-band width...
... bigger cylinders, increase power, but lower the potential peak RPM...
... and increased compression,.. packs more fuel, and thus more heat, in whatever size chamber you use...
(and this affects reliability, and longevity)...
So,.. you trade one, for the other...
Peak HP... top speed...
Torque-band,.. pulling power...
Heat/longevity,... compression, chamber size, RPM, flow...
You design the engine you want,.. for the job...
... or something like that...
...