Thanks Seraiel
I've kept GP production in mind and am running the 'right' type where most appropriate. A big issue is that other cities can't beat the GE city to 3000

however, so I need to hold back some others. Otherwise I tend to hire an engineer first, and then merchants. I've also hired merchants where scientists are perhaps better, because I need money. Haven't completed either Hermitage or Moai yet, but even if I got 10,000

for it (will be much less, at a guess), it would only allow research for 4 turns. Crazy stuff
What I'm doing now "feels wrong", but not sure. I have gone back to caste to be able to run specialists instead of growing onto unimproved tiles (even with 100+ workers they can't keep up everywhere). But I also have a GS, GM and GSpy for a GA, which would make economy and GP production faster. However, I figured I needed a GA later when needing to switch to slavery when Mining finally comes online. It feels a bit backwards, though, to run caste and specialists outside of a GA, and then move to slavery when in GA later. Given I need the 100% GE next, however, I won't get enough new GPs for a 4GP GA, and I should probably hold off on that GA until space parts.
A micro nightmare right now tbh, so many settlers and boats moving around, and trying to plan for a war on Pericles too, who has over half his cities offshore. I try to take my sweet time and make more good decisions than bad ones, but it's simply impossible to plan and play perfectly with so many moving parts. Could perhaps managed some galleon-galley chains here and there, but it's too much. Last turn still took two hours. The one before that a lot more due to GA coming to an end.
Haven't spread Sushi to islands yet (just one), but will try to do some of it when most planned settlers have got in place and the mainland has got Sushi. Some new/conquered cities don't have courthouses, though, so can't really give those Sushi yet.
Will take a look at the save you mentioned, and quite possibly ask more questions
Lately it seems like the fall has flattened out and we stay at roughly 10% for break even. Have a few thousand

in the bank (keep hoping for inflation event), so the +~300

per turn at 0% pays for Sushi spreading.
Looks like pre-whipping executives work well btw. You just need to make sure max four are alive/in queue. Spreading will still be slower ofc due to increasingly longer distances (can only pre whip one exec per city), but it should still be faster than slow building them.