Seems it would do the same where ever it is since wavelengths are so big.
Yes. This is exactly correct. Moving a sub around merely moves the modes around. They are still there, just different locations.
This is why locating one sub is so frustrating. Moving the sub changes nothing fundamentally, but it does move the peaks and dips around. This is why the Distributed Bass Array works so well. The peaks and dips are still there but with four subs each one is a little different and so all together they add up to smooth response. Smooth bass is fast bass, and so its also incredibly tight and articulate.
With four it doesn't hardly matter where they go. Usual approach is along the walls, one near each corner, but asymmetrically a different distance from each corner so as to create as many different modes as possible.
That's the frequency response aspect to it. In terms of imaging, timing or whatever you want to call it, then definitely what you said, does not matter.
