If FFS leads to more caught fish, any species, it will also lead to more fish dying due to handling. Thinking specifically about gills swallowing hooks. But musky has to high on the list as well. Taking them from the thermocline is a bad idea. Fishing and catching when water is hot isn't the worst because they are already in that water column. Just gotta handle them carefully and try to water release if you can.
I do have FFS. I do use it for eyes and bass on the Bay. I don't catch "more", but I do catch them more efficiently, for sure. And I do know where the fish are. I can tell you this...I love using MegaBass jerkbaits. I love the baits, I know fish love to eat them, but they are awful baits when you look at how they hook fish, and hooks scrape around the fish in the net. It isn't uncommon to bring in a small smallmouth and have one treble in it's mouth and another one or two sticking the fish elsewhere.
So logic tells me that if I really dial in my FFS and I'm using megabass....I'm hurting the fish more.
If i'm using wacky worms, or if my wife uses wacky worms, she tends to "feed" them. And getting the hook out isn't easy (on her fish). So again, if I'm finding more fish on FFS and not being careful with my presentation, yes I'm harming more fish.
And I have not and will not sharp shoot muskies. What I will do sometime is drive around with FFS and see if I can see suspended fish. I need to see if it works that way where I fish. But I'm not going after them. I've caught enough in my life to not have a need to do it that way.