I actually find the Golden Age kinda fascinating because I don't really think there's a split at all. Clark = Superman. And I dont think we've ever really seen that kind of fusion since. I mean, Clark works at the Planet to serve Superman's mission, and his personality is all Superman, but that's who he grew up as and was raised to be. Many of the personality traits we now assign to Clark, such as being shy or socially awkward, just weren't there at all except as a thin disguise Clark often forgot to maintain. I think, in a way, the Golden Age's answer to "Who is Superman?" is "Both." The writing back then just wasnt advanced enough to handle the kind of psychological split we see these days.
How are we defining the modern Age? I definitely agree post-Crisis began with "Clark is who I am" but I think they were shifting towards "he's a mix of both" by 2000 and trying for a more even split. What I find interesting is how poorly that actually worked. A lot of effort was put into re-inserting the pre-Crisis elements but no matter how hard DC tried, it just never worked for that version.Silver Age/Bronze Age: Kal-El
Donnerverse: Kal-El
Modern Age: Real Clark (and eventually a bit of Kal-El)
Really? I myself think the New52 was very much "SUPERman" over "superMAN" in most regards. There was definitely the "he's a bit of both" happening, as modern writers like to do, but I always got the feeling that Nuperman was very much Superman more than Clark. I mean, its semantics, as has been said, and obviously the "Clark" side of his life was very important to him, but I always thought that Clark was far more of a disguise (or perhaps I should say who he was forced to be in order to fit into society) than in post-Crisis, and that mixture felt far more organic and natural than the post-2000 efforts of pre-Flashpoint.DCAU: Real Clark (and eventually a bit of Kal-El)
New 52: Real Clark
I think Bendis is writing a more even split than Tomasi did, but largely I agree here.DCEU: Real Clark (with a hint of Kal-El)
Rebirth: Real Clark (with probably a bit of Kal-El)