... so you are saying that district discounts of a few districts is more efficient than pre placing?
There have been many threads about it being pointless to build cities after T100 which I disagree with but your key cities need to be in place by then unless you are playing longer than T200.
The strategy of a 2 phase empire I used to play well over a year ago where you build a few key cities, get them working then expand in a second phase just does not work as well.
One of the important things is population, as a city grows in size it takes longer for a new pop. More cities earlier just works..
I don't know. I'm not sitting here with a pen and make notes every turn.

I like to play peacefully as much as I can and just share what works for me. I don't restart until I can spam cities and win on T200.
Growing cities to size 10 isn't much of a problem with Audience Chamber and harvesting jungles/marsh etc.
If done carefully, district spam means that only your first 2 districts aren't discounted and then only one district of your choosing, probably campus most of the time. The rest will be discounted almost through the entire game. So basically you only pre-place one type of district. Obviously, civs with a unique district have an easy choice there. Japan, Germany, Russia and Korea are arguably the best civs for this district spam. Followed by Greece and England.
If you want to play peacefully, it's pretty awesome. The 2nd expansion wave can be optimized by getting a religion which guarantees the medieval golden age on turn 88 (most of the time on Deity). Rush Feudalism and faith buy buffed builders and settlers.
Or ignore religion and get more trade routes and campuses instead. Works both. With a religion, you'll have better infrastructure, less science and more culture but you can catch up with insane Moksha Apostles and get +1 science per religious follower in foreign cities.
Edit:
Just had my fastest win with this strategy. Germany, Deity, standard. Peaceful science victory on turn 221 although I was too lazy and tired to really optimize the late game. For example I forgot to rushbuy the space port with Reyna although I had the promotion.
I only had 7 cities on turn 100 but had another big wave of settlers during the renaissance golden age with Hic Sunt Dracones. Around 100 districts and 20 cities in the end

Here's the graph of total districts constructed.

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