https://www.reddit.com/r/AskHistorians/comments/7hawn2/ama_ancient_egypt/
/u/cleopatra_philopater talks about the role and function of the pharoah (its near the bottom)
I mostly skimmed the AMA since its really long but you might be interested in other stuff talked about the inside
/u/bentresh gives a long overview on ancient egypt and how it changed through the centuries
I hope these help answer your question!