This common name refers to only one family.
These are very rarely called Giant Sedges.
This huge family
appropriately contains huge caddisflies. Many of its genera are important, but the western genus Dicosmoecus
(the Giant Orange Sedge or October Caddis) is especially important as a big-trout hatch.
contains so many species that it is difficult to generalize about them all. LaFontaine commented on the task in Caddisflies
The fact that fly fishermen need broad principles of biology, not a collection of exceptions, makes it difficult to handle this family.
I recommend learning which genera or species are prevalent in your area and studying them specifically.