Nero might have SGLed (or MGLed in Vanilla) The Great Library, Bach's, Shake's, Newton's, the Sistine Chapel. He also could have not SGLed any of
those high culture wonders and still had the expansion. He might have accomplished this by "building" two buildings in one turn. Unless I've missed something the maximum amount of culture obtainable in two turns is...
In terms of city placement for space games I recommend two basic principles that you use, and that you worry less about a spacing scheme.
1. Place cities based on terrain. Found on rivers. Found next to lakes. Jam cities into the coast so you can maximize commerce from sea and ocean squares (and build commercial docks). Found on hills to maximize food. Found on brown instead of green if they lie next to each other to maximize food.
2. Make sure that every square within your cultural borders can get used by some city at some point. If you have a square which can't used by any city even with a hospital at some point, then found a city on or around that square so that you can use it.
If you get hospitals and feel comfortable with your production level then I'd add this...
3. Irrigate *all* squares once a city has hospitals and turn any specialists you gain into scientists. Really, under most circumstances turn all specialists into scientists.