Can you record the sound around the chassis with the pump on? There is definitely vibration, the main question is how is it dissipated, it is a very important question as many people who bought the case are approaching it from a silent build perspective.
Much depends on the surface on which you will rest it, for example,
I have a wooden top covered with a brocade cloth which, in addition to allowing me to freely use the mouse on the entire surface of the desk, attenuates any vibrations and various noises ...
...the best test for you will surely be what you will do at home with all your variables,
I can tell you with that: with pump at 5 (maximum) > zero vibrations and zero noises, both with and without feet
(nb: the feet were 4 feet stolen from an old vhs reader)