Yes it does a difference. I live un France so i'm in CE area and have a really bad range on 5.8ghzIn a CE area... does this do anything at all for the 5.8ghz?
A simple test i did :
Icarus software boost 2.4ghz but doesn't change CE to FCC... i had a strong video signal (2.4ghz) but always poor range on rc 5.8ghz...
With Power magic i have the same strong signal on vidéo (2.4ghz), but now i'm able to fly my P3S to ~2km in the same area. The différence is i use FCC setting in Power magic (so 5.8ghz is set to fcc power) and telnet command "iw reg get" confirm that. With Icarus "iw reg get" give me CE ...