Which is the actual identity, Superman/Kal-El or Clark Kent? Does Superman/Kal-El disguises himself as Clark or does Clark disguise himself as Superman/Kal-El? Which is the real person?
It depends on the era. From 1938 to about 1987, the standard assumption was that Superman was his real identity and Clark was just a disguise he donned for convenience. In the comics, though he didn't initially know his origins, it was gradually retconned that he had a full photographic memory of his infancy on Krypton and full knowledge of his past and heritage, and that he'd been operating as Superboy throughout his adolescence. He kept being given more and more ties to Krypton -- Supergirl, Krypto, the Bottle City of Kandor, the Phantom Zone villains, lots of time travel stories -- and his Kryptonian identity became more important than his human facade. The radio, film, and TV adaptations didn't go that far, but insofar as they addressed the issue at all, they tended to treat Clark as the disguise. Radio Superman Bud Collyer was one of the few Superman actors who really gave Clark and Superman distinct voices, and in a radio storyline where Superman lost his memory, the voice he defaulted to was Superman's rather than Clark's. (Yet somehow, when Lois and Jimmy discovered him working as a record-breaking baseball pitcher, saw him without his glasses, and heard him speaking in Superman's voice, they recognized him... as Clark Kent. But not as Superman. Sometimes the radio show was really, really dumb.)
But when John Byrne rebooted the continuity in 1987, he inverted that. He reasoned that if Kal-El had grown up as Clark, then Clark should be his primary identity. He had Clark grow up not knowing about Krypton or his true origins, and only gradually developing his superpowers as he grew up, so that he had far more ties to his Earthly identity. He had Clark perform heroic feats secretly and in plain clothes, only adopting a costume after he'd been outed -- an approach emulated by
Lois and Clark: The New Adventures of Superman,
Smallville, Man of Steel, and even the current
Supergirl series to a degree. As Clark explained to Lois in a
Lois and Clark episode where she (temporarily) learned his secret: "Superman is what I can do. Clark is who I am." L&C embraced the idea of Superman as a public persona that Clark adopted so he could help people without jeopardizing the everyday life as Clark Kent that he valued so much.
Byrne even flipped the traditional romantic triangle: Instead of Lois longing for Superman's love and feeling contempt for Clark, now Clark was Lois's romantic interest as much as, or more than, Superman. Again, this was the formula
Lois and Clark followed, as well as
Smallville (obviously) and MoS.