What is "Game ISP"?
If it's ROG GameFirst then you can disable or uninstall it. It's only useful if you're splitting your network bandwidth across multiple apps (say, playing one or more windowed games, streaming music, and updating/uploading/downloading or P2P filesharing in background) - it's just useless bloat (which consumes resources and impacts performance) if the only thing you're doing on your network while you game is playing your (one) game.
If you're referring to congestion on the game ISPs - the actual game servers - then there's nothing ASUS (or your hardware/software configuration) can do about it. The network performance bottlenecks are on the Square Enix or Blizzard servers. Pick a different server or play some other game, if you can. Submit a bug report, complaint, or other user feedback if it makes your gaming consistently unplayable.
You can run netstat to monitor your active network connections, performances, and pings.
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