So another thing that matters in optimizing the turn efficiency is when you build your CS. lets say you are playing primary and going for 50k acres, after a 4k acre tech start. That means the most turn efficient way to get there is to build 460cs straight away, then build your 3.5k labs, tech 200 turns, switch, then grow and build to 50k acres. Thats optimal turn efficiency.
The problem with this is that you run your 460 turn building CS at a very low income.
The way people used to go about this is they would run lower than optimal turns for the tech phase and perhaps a little lower bpt as well, then right after the tech phase they would build a bunch of CS, maybe not all they need for the round but a nice chunk.
So if instead you build 160cs before the tech phase and 300 CS while you are a high tech 4k acre casher you make maybe around 500-600 million more cash with those turns.
What is best will depend on server and perhaps market conditions. But these are the things you should have in mind.
I remember there were some very good discussions between some very smart people and a lot of math and experience went into it that the optimal 300 turn tech start was about 100 turns of teching. Because the same math applies you will generally want the same 1/3rd of your turns, as you get switched, to have been teching turns or thereabout. If you end up teching more turns, you would have been better off teching at a higher acreage, mathematically.
Ofc stuff like being a target, when its feasible to mass-explore and tech prices plays a role in those decisions the answer might not always be exactly that, but certainly this can be used as a guide.
So if you do a 3800 acre tech start, which is standard, you might wanna be switched something like turn 540 wiith 180 teched turns as a standard. A lot of players tech too much for their own good, and it also hurts the function of the market.