"anything they purchase beyond OFC at the proper gauge for the length isn’t going to change the sound"
WRT the conductor material, I tend to agree. Ambient noise in just about any room is going to overwhelm a 1-2 percent difference in the conductivity of OFC (about 101% IACS) vs. OCC copper (about 102/3% IACS), or even a 5 percent difference between copper and silver (about 105% IACS). I also truly doubt the human ear can reliably discern the difference between standard annealled copper and OCC or other exotically drawn coppers that reportedly have fewer grain boundaries, especially considering the ICs and speaker cables containing those metals are nowhere near the only metals that a music signal passes thorough on its way to being a sonic waveform that we can hear. However, that doesn’t mean that I don’t have OCC copper cables in my system, because I do. Note that the respected Galen Gareis of Belden uses ETP copper (100% IACS) in one form of his signature Iconoclast cables.
I do seem to reliably hear subtle differences between different cables, which I doubt is due to the metal material but may be due to the conductor form, i.e., solid core vs. stranded, conductor diameter, cable geometry, dielectric materials, and/or other factors, or maybe just a figment of my imagination based on my bias.