Speaker reponse graphs are data, and ONE tool, for evaluating SPEAKERS. There are other factors, such as harmonics, impedence changes, speaker coupling if in a mutiple speaker cabinet, back of cone wave reflection emphasising or cutting certain frequencies, etc. However, NONE of those other factors change what the curve on the graph is telling you. They just add another influence. So for SPEAKERS, the actual thing that generates the sound, intalling them in YOUR cab, hooked to YOUR amp, with the amp EQ optomized for THAT DRIVER, is the final and best test. However, time and money (but I repeat myself, because time *IS* money) being limited, speaker response curves and other user's anecdotes in similar applications can steer you in the right direction, rather than buying (at $150 - $200 a pop) ALL POSSIBLE SPEAKERS for trial. Not a real option for most of us in the real world.
Now when it comes to speaker and power CABLES? A much simpler problem for physics and material science. And also one where Occam's Razor correctly guides us to the appropriate answer - the simple one.
Don't believe me? Look inside a Marshal or Mesa Boogie cab - and see what kind of wiring connects the speakers.
https://www.chicagomusicexchange.co...960a-4x12-guitar-speaker-cabinet-1978-1705641
https://ca.pinterest.com/pin/mesa-b...-g12-vintage-30-speakers--144467100516280385/
Oh, and as to my "7th grade science" brain? I have a 4 year STEM degree with a minor in mathmatics. 1 year of vocational electronics. I have hand-built a tube amplifier, including forming the chassis. I am a former (and hopefull soon once again) gigging musician, and currently a data center analyst for a hospital. In the course of my daily job, one of the things I deal with is power and power cabling. Systems generating literally millions of dollars in revenue and upon which patient's lives depend are racked and connected to power with .... the factory supplied power cable, or it not, one different only in the color of the outer insulation such that we can keep track of which independent power source each power supply (most devices have redundant power supplies) any particular power supply is cabled to.
You having noise issues? Especially at a gig where the stage area electrical was installed by the bar owner's drunken brother in law in exchange for free beer? A noise filtering power condition, installing ferrite slugs on your power cables, and TURNING OFF THE NEON BEER LIGHTS near the stage will get you a lot further down the road than "high end power cables". And if my suggested steps don't completely solve the problem, a noise gate, specifically a linked two channel noise gate using the four cable method on your guitar amp, will do a lot more than a high dollar power cable.