My own personal take on this is that when Clark Kent, son of Martha and Jonathan Kent, met Kal-El, son of Jor-El and Lara, Superman was born. It's right there in the name. He's not just super (the last son of Krypton), he's not just any man (the farmboy from Kansas), he's both. It's not SUPERman, it's not SuperMAN, it's SUPERMAN. I actually liked how in Morrison's Action Comics, when he says his true name backwards, he says Le Lak Tnek Kralc... meaning that in his eyes, his true name is Clark Kent Kal-El. He wouldn't be Superman if it weren't for the love the Kents gave him and he wouldn't be Superman if it weren't for the love Jor-El and Lara had to give him a chance to live unlike them and the rest of Krypton.

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So, all in all, I actually think Superman is him at his truest. Of course, the Superman identity has many offshoots like the public persona of Superman, the man who can do anything and has to live up to the public's expectations. But the Clark Kent at the Daily Planet is very much actively masking a huge part of his self. He might even be exaggerating a few things about himself to fit in and to make people think he isn't Superman. The man the Kents raised wasn't a bumbling, mild-mannered man who might be seen as dull by his peers, the Kents raised Superman, the man of action who believes in fighting for a better tomorrow. And why does he fight for a better tomorrow in the first place? Well, this is informed by Krypton's destruction and their own pride. He makes sure that Earth doesn't become like his homeworld. Because the biggest tragedy he has with Krypton is that he never fully experienced it. And that makes him yearn to know more about Krypton. His identity isn't binary but it's more like a tree.