Some minor differences at this point, but all vehicles sold here (new) have to meet the CA standard regardless of county. Some areas used to be easier or less frequent on the smog checks, but I think most of that is gone now.
Sellers are responsible for getting the vehicle smog checked before sale. IMO the only reason to buy a car without a smog here is if the registration is current, you are taking it out of state and will have no inspections and you are planning on some kind of rebuild, rework, repower whatever anyway.
In some cases, you might find a real deal on a late '70s or even well into the '80s vehicle where the owner can't make it pass smog and doesn't want to scrap it or doesn't qualify for the state give-away. Probably an unusual circumstance, but not impossible