Some random things:

1) Billy Batson and shapeshifters are two such examples of comic book characters who should have pretty strong secret identities, but the catch was that they just had to make sure nobody saw them transform to and from their superhero to civilian identities. I also think characters who wear full masks would work, but like the first two examples, eventually the weakness in their plans to hide their identities from the public would be shaking spies and other snooping people off their trails so that they don't get tracked to their secret headquarters/homes/whatever. If Spider-man and Batman really existed, they'd eventually be found out, not because people can see through their disguises, but because eventually someone good at spying will eventually track them down.

2) About the nickname "Smallville": I went to high school in Peoria, Illinois. It's not exactly a tiny town in the middle of nowhere, but a bunch of suburban kids from Chicago liked to think it was practically podunk, filled with nothing but cornfields and cows. Two girls I knew from college both independently (as in they probably never met one another, even until now) started calling me "Peoria" now and then. There was never any malicious intent involved. Maybe they were a little snobby about small towns, or maybe they just thought Peoria had little to offer in terms of being an enjoyable place to visit or live, but all in all I knew it was just good-hearted ribbing. The irony, though, was that I spent most of my time living in the Chicago suburbs, but why bring that up and ruin their joke? I figured Lois' "Smallville" was the same, except maybe Lois was a little flirty about it whereas these gals were not flirting, heh. I'm sure in Earth-63, where baby Kal-El's ship crash landed in the Metropolis burbs, and Superman moved to Smallville and met country gal Lois Lane, she'd just call him "City Boy" or something. Considering that the "Smallville" nickname is often credited to Dana Delaney's Lois from STAS, I feel like if you actually watched the show you'd understand it's not a nickname meant to be cruel. That Lois is a little bit snooty when it comes to country folk, but it's just part of the characterization. She's no nonsense, and I think it's also almost militaristic, too. IIRC, this Lois was also an army brat, and her "Smallville" comments are almost like a drill sergeant's randomly chosen nickname for a new trainee. Cartoon Lois' impression of Clark is that even though he was hired to be her partner, he was clearly less experienced at reporting in the big city environment, and being hard on him was mostly her way to toughen him up for his own good. She was also naturally impatient, and easily frustrated, but Clark Kent can be a frustrating guy, often times intentionally.