For me speaker cables, then the XLR interconnects, where the biggest improvements. But everything i coated got better and was noticeable.
This stuff according to everything I have seen is a lot of the same ingredients as TC with probably the biggest difference being the solvent or carrier base, which is more oily than TC. In terms of effect everything everyone is saying is right in line with it being a TC knockoff.
This being the case, what you will find, it can be applied with equal improvement to the outside of internal speaker wires, speaker magnets, basket, and crossover parts. The effect is good in a lot of places but even better around higher voltage swing type areas like speakers.
You do of course want to be extremely cautious as this is highly conductive. That is why they plaster warnings everywhere. But as long as you are extremely careful then it can be used to good effect on the outside of AC wires, around the inside of outlet boxes including conditioners, on transformers, caps, and circuit boards inside components, on and on.
Keep in mind the stuff is expensive. Painting it on the outside of something like a speaker cable, that stuff is gone. That is why I prefer whenever possible to paint on something removable like fO.q tape. That way if you ever sell or change your mind just peel the tape off and use it somewhere else, you still have the goop.