When we change something, we can hear a different sound. We hear stuff on recordings that we may not have noticed before. Sometimes we may lose something in the process, sometimes not
Sums it up pretty well.
I think that's what most of these "tweaks" or even changing amps, Dacs, etc.. (leave out speakers and room treatments for now) do. For instance cable upgrade, changes LCR, emphasizes certain frequencies , we wax poetically about new cable, hear things never heard when actually they were always there. Once our brain gets use to new cable switch back to old, hear things never heard before.. etc.. 95% of what we hear is speaker and room interaction.
As long as everything else operates within its given parameters, dacs, amp, wires, concentrate on good speakers with a nice even FR , fix problems with room best you can and DSP to taste.