Do good power cords have to be stiff?

I’ve also read from a few manufacturers that if your power cords seem too stiff, it might be that your equipment is too close to the wall, and there are lots of nasties in wall you don’t want too close to your gear...

Less Loss cables, made in Lithuania use a braided construction and are extremely flexible.

Stiffness of a power cord has no effect on the sound. It only changes the mechanical characteristics and makes it easier to handle. As long as the current rating of a cable is not exceeded, the rest does not matter electrically & sonically.

Simple answer… NO!
 

I was using Nordost Vishnus in my mid level system. A clear improvement over stock.  But they too were somewhat stiff. Replaced them with Morrow MAP3s which sound just as good as the Nordost and are quite flexible. If I get the upgrade itch I will climb the Morrow ladder before going back to stiff power cords.