It's relatively easy to settle 4 cities and finish NC at turn 90, so in my opinion two fewer cities is way too much of a sacrifice for 10 turns earlier NC. Besides, why focus on killing your start to build a shrine and gaining a pantheon so much, or even at all, if your entire game-start is based on racing to Education, rather than settling cities. Religion has little to offer a two-city empire, nor a late-blooming four-city one.
A library in the capital, in the turn/population range between when you are building it and turn 90, gives you yields such as: 4 beakers. There's no reason to build it before the second and third settler. Plant 2 more cities and they will give you 4 beakers within 7 turns. What I'm saying is building library in the capital, way before the other cities are about to finish theirs, is not worth opportunity costs.