Powercords have improved the sound of my components considerably. The DAC for sure, the greatest impact on my amp. But the influence also depends on the power cord design. Some are made for components, where noise reduction over low resistance (big thick conductors) dominate and visa versa. The design also determines the tonal balance effect… so different cords may impart a tonal shift… like Cardas towards warm and Transparent and AudioQuest little to none.
I have an scientific and engineering background… and was employed as both. The first thing I learned was to quickly locate the limit of science in explaining and then start observing to determine the outcome.. Didn’t take long for me to drop theories that should impact sound and just listen.