This is a good write-up but it's also missing huge other sections of quant finance like statistical arbitrate and factor investing. I guess you could put this under the 'market taking' section except everything he describes is still in the mode of single stock thinking while these strategies are more about portfolios. You typically estimate some factor model of the market and use a portfolio optimizer to create your trade baskets.

In these types of strategies you care about latency but on the order of milliseconds not microseconds. The challenge is in building multi-day predictive alpha models with low correlation to each other, getting good executions though brokers can do a reasonable job these days, and especially combining alphas into one book which requires sophisticated mathematical programming (conic programming etc)