Ran a few tests. Sorry for the rough write-up, I was in a hurry.
Tech path throughout all: BW -> The Wheel -> Pottery -> Writing -> Iron Working (placeholder)
First test
Builds: WB -> part WB -> Worker (
whip) -> finish WB -> Settler -> Library -> Granary (placeholder)
Second city founded on turn 42 (
+2 delayed from second test).
At start of turn 42, have 36 hammers into the placeholder Granary (
-18 loss from second test), and 253 beakers in the placeholder Iron Working (
-16 loss from second test). No hammers yet produced in second city (
-10 from second test). Exploring Work Boat has moved
2 tiles further than in second test. Worker has chopped 2 forests (
same as second test).
Second test
Builds: WB -> part WB -> Worker (
no whip, no Slavery) -> finish WB -> Settler -> Library -> Granary (placeholder)
Second city founded on turn 40 (
-2 quicker than first test).
At start of turn 42, have 54 hammers in the placeholder Granary (
+18 from first test), and 269 beakers in the placeholder Iron Working (
+16 from first test),
plus 10 hammers into a Work Boat in the new city. Exploring Work Boat has moved
2 tiles less than in second test. Worker has chopped 2 forests (
same as first test).
Once again I would like to emphasize that we do not
need to switch to Slavery anytime soon. After the building of the Library our capital is at size 4, and we want to grow it to size 6 and keep it there ASAP for the dual scientists. We won't need to use the whip for some time, so there's no sense in wasting a key early turn in anarchy.
I was thinking for a moment that we'd need a Monument in the second city, but then remembered we're Creative. That trait definitely comes in handy! Allows us to start straight on the Work Boats, given that both the Fish are in the ocean.
Out of interest I tried the Worker first too.
Third test
Builds: Worker -> WB -> WB -> Settler -> Library -> Granary (placeholder)
Second city founded on turn 39 (
-1 quicker than second test).
At start of turn 42, have 51 hammers in the placeholder Granary (
-3 from second test), and 321 beakers in the placeholder Iron Working (
+52 from second test),
plus 15 hammers into a Work Boat in the new city. Exploring Work Boat has moved
8 tiles less than in the second test. Worker has chopped 4 forests. Also note
capital is at size 5 (was still at size 4 in previous tests).
So in essence, either way I prefer no whipping - thus it comes down to the second test or the third test.
Summary
Going Worker -> WB.
Pros: Gives us significantly more beakers (in excess of 50 extra); it allows us to found our second city a turn earlier (thus giving us 5 bonus hammers); it means the capital is at size 5 (and consequently size 6) a few turns earlier.
Cons: We have chopped 4 forests rather than 2; our exploring Work Boat is 4 turns behind the other option.
Going WB -> Worker.
Pros: Gives us a 4 turn bonus in exploration; gives us about the same amount of hammers but leaves us more forests still to chop.
Cons: Extra turn to found the second city; much less beakers produced; capital growth is a few turns behind (still size 4 at turn 42).
After all that, would you believe I'm still undecided.

I'll sleep on it and come to a decision in the morning. Basically if we go Worker next we're trading off a few turns of exploration and a couple of forests for a whole lot more beakers and slightly earlier/larger cities. On the other hand, if we go Work Boat next we're trading off a whole lot of beakers and a couple of turns of city growth for faster exploration and more hammers in the stockpile for later (from chopping forests).