Although peng must be inherent at all times, it can also be expressed. Manifest peng delivers power upward and outwards.
Imagine a Swiss ball? One of those large round exercise balls?
If somebody were to roll you off to one side using a Swiss ball, that is what manifest peng feels like.
It has give and is springy, yet it is also substantial.
Ever martial application in taijiquan relies upon both inherent and manifest peng.