Power cords absolutely do make a difference. Call it shielding, geometry, materials whatever it is... I'm just glad the cord I settled on is cheap ~$5 14AWG shielded and readily available.
Other quite a bit more expensive cords also made a difference just not all positive in my rig so the $350+ was hard to swallow. But they did make a difference.
For filtering, less is best. I like the Monster 1000 series for no nonsense minimalist filtering and isolation. Anything more and it chokes the gear. What I'd really like is a power bar like the Hammond or PS Audio without filtering but with surge protection. No one seems to make that. You want surge you get filtering, no filtering well no surge.
Touching base on a few other claims... Romex is actually very fine power cable. If you cut open some audiophile retardly difficult to flex cable you'll find Romex in a new dielectric. Actually one of the more effective DIY cords is a Romex braid.
For the physics and electrical gurus in house, I'm going to go out on a limb here and say you're likely bachelors of X and not PhDs active in the field of conductor development. Might be wrong but generally the my textbook says types are students which makes them at best someone with the potential to know more than the jist of it someday. Today though, all you know is the bare bones minimum they tell you so that the world makes sense