I'm embarrassed to say with all the fishing I've done since being a little kid, I never tried to Filet a fish. 🫢 All my fishing is done on party/ charter boats.
I have always used a 6" Dexter for everything from flounder to tuna. (I do like a 9" to carve a turkey.lol)
I use a pull through sharpener on the water , a steel at the dock and a stone at home.
Many guys over use the pull through. A sharp knife only needs 1-2 pulls to keep the edge.