Who is NSA’s customer? What is their purpose? Does congress and the FBI have access to their intercepts?
NSA’s customer base is all concerned governmental agencies (including the WH) which agency gets what depends on the Intel, origin and nature. Congress has no access except as elicited by hearings (closed) before Intel Committees and the like. FBI might get info pertaining to foreign agents working in the US - that sort of thing. Most Intel goes to DOD and Pentagon, Army, Navy, Marines, Air Force, and other spooky agencies.