And, btw, you are giving bad advices. You are wrong here: "By default, nginx sets our keep-alive timeout to 75s (in this config, we drop it down to 10s), which means, without changing the default, we can handle ~14 connections per second. Our config will allow us to handle ~102 users per second."
No, the keepalive connections doesn't limit nginx anyhow. Nginx closes keepalive connections when it reaches connection limit.
"gzip_comp_level sets the compression level on our data. These levesls can be anywhere from 1-9, 9 being the slowest but most compressed. We’ll set it to 6, which is a good middle ground."
No, it's not "middle ground". It kill performance of your server. With 6 you will get 5-10% better compression, but twice slowness.
"use epoll;"
What's the purpose of this? The docs says: "There is normally no need to specify it explicitly, because nginx will by default use the most efficient method."
"multi_accept tells nginx to accept as many connections as possible after getting a notification about a new connection. If worker_connections is set too low, you may end up flooding your worker connections. "
No, you have completely misunderstood this directive. It isn't related to worker_connections at all.