My questions isn't necessarily about a specific type of game or situation but rather about where to find resources to study and have an in-depth understanding about networking in online fast-paced action games.

These resources can be about synchronization, relations between networking and client game systems (physics, rendering, etc.), client-side predictions and basically anything that would be helpful while designing and creating a fast-paced action game that involves networking.

I don't know of one, omnibus resource for this.

Most of the integration with physics/rendering depends entirely on how your game itself works, which means that a solution that works for, say, Street Fighter, probably won't work for Forza, and what works for Forza might not be right for Overwatch.

Gabriel Gambetta has a series on his network engine “GGPO” that he used for fighting games. He tends to believe that the entire world is a nail that's fit to that particular hammer; that's not true; but that hammer is fine for what it does, so you can look at that.

Gaffer has an article about “Zen of Networked Character Physics” that's also pretty good; you definitely should read that.

There was a YouTube video from some developers on the networking team on Overwatch at Blizzard, that you can probably track down; it talks more higher-level about how they solved specific gameplay-related situations in that game.

Good luck!