What changes if you scale Young's and applied pressure by the same amount. Why?
Both Young's modulus and applied pressure share the same units (let's call them pascal in this example) - force over area. While area is present in the simulation though the dimensions of the simulation cell, force does not show up anywhere else. So scaling Young's modulus and applied pressure the same way corresponds to selecting a new choice for the units of force. The output in terms of displacements will be unaffected in that case.