Observations so far are a little strange (with 40.13) actually, which is why I was asking since I'd already done experiments but not been successful, and wanted to know if I was missing something abrasively obvious.
My tests were: I took a world design that I put together in PerfectWorld, and repeatedly did 35 generations (only 10 years) with that as the basis, whilst keeping all seeds except the world seed. My main test to save time trawling through entries was checking the first human civ's gods, and checking out the artifact slabs. However, the names and history appear to end up different each time when checking them in Legends mode- which civ is placed first varies, and the artifact slabs vary wildly within the conditions that there is always 1-3 of them and they are always raised by demons.
However, as one might expect, keeping ALL the seeds including the world seed results in a carbon copy world. I only did this twice but it was quite obvious.
I guess that the simple conclusion from this is that the world seed also affects history and name generation. Which I guess in some ways makes sense for the history; even with a perfectworld basis, rivers and volcanoes and minerals and lakes and such will be generated in different places; so settlements will spring up differently. But its a little bit of a shame for people wanting carry across their favorite gods and stuff, like this:
Haha. As you might guess, I wanted to keep the Glacial Confederacies and their cool gods (there was also 'Ok, the god of revenge', and 'Sol, god of the sun' in their line up which was amazing!). Ah well...