Simple multiplayer game mode rules?

Referencing the multiplayer shootout game, there is some great functionality for blueprint networking- something that I feel is the one area where blueprints could be buffed. However, there isn’t any game ending event or time limit- I have read that these kind of things happen in the GameState blueprint. If you were to set up a basic system so that when score = x the game ends, or when when the time runs out, the game ends, how would you implement that? (What would keep track of all the scores and decide who is a winner?) Also on the note of a game clock- how would you actually achieve that? Set a timevar -1 every second until it reaches 0?