-I don't think all Kryptonians are naturally immortal with or without the sun. That's always rubbed me the wrong way. Long lived as hell? You bet, but immortal seems a little iffy to me.
-I don't think Kryptonians should be be decedents of gods or whatever else people are trying to come up with to make Kryptonians this race of "chosen ones." I think they're just a really really advanced human-like race, and their achievements make them well known throughout a large bit of the galaxy. If they're "chosen ones" then it hurts the metaphor of their achievements being well within humanities reach if we only dig deep and get over themselves. Both All Star and American Alien have it write. We're all in this together, and we're all just tiny aliens clinging to rocks.
-I think Supergirl should be more book smart than Superman. That's not to say Superman is a fool or whatever. He's still super clever/smart and is very a talented engineer, but Kara lived on Krypton for 16 years, and her brain has only been boosted in processing power since she got to Earth.
-I think the reason Kryptonians get such a substantial boost in power and ability depending on the sun is because of simple cosmic happenstance. I'm a firm believer in the "photonucleic effect" and the absurdity of it
http://superman.wikia.com/wiki/Photonucleic_Effect
-I think Clark should actively be working on the case files of all of the Kryptonian Phantom Zone inmates. I think he should set the possibility of parole for some inmates. I also think he should scheduled telepathic one on one meetings with each inmate to correctly evaluate. I think Clark should be deeply conflicted with Jor-El inventing the projector, and it should give him a sobering look at his second culture. I also think Clark should come into conflict with a number of JL members, and even Lois to a degree on his choices with the PZ criminals.
-In contrast to my top opinion, I think Superman through some other means (DC 1 million sees him travel all of creation, and come back presumably with his immortality) can become basically immortal or just more long lived than the already astonishingly long life he would normally have. TAKE NOTE: I don't think his immortality should come from something already inherent to him or the universe keeping him alive of some sh!t. IF he were to be immortal, it would be because of some ridiculous and harrowing adventure he saw his way through. He's not "the chosen one" or inherently special outside of just being a fantastic person. He's just a very nice guy who happens to have the strangest life possible.