Like so many things in this hobby there appears to be no simple answer to power conditioning. And apparently there are various types of power problems that can be addressed.
my goto reference for this is live testing done by alpha audio which you can watch where they both subjectively and objectively show that different conditioning devices work better in some situations better than others and in some devices better than others and ‘conclude’ that the results are situation dependent and you must try the specific devices in their intended places to know if or how much they will help.