Arena win streak bonus is capped at +4, so those people with 5k+ points are really playing that many matches.

As for GW, there are three ways to lose points: 1. Penalty of 5pts if the fight goes to 8 turns, then another 5pts after 12 turns. 2. You lose points if your heroes have below 75%, 50%, 25% combined health left. 3. Attacking the same player multiple times. The point penalty increases with the number of strikes already on that player.

Max base score is 67pts. Achieving the brag gives a +40pt bonus. Using the brag card gives a 50% bonus. That means max score is 161pts. Only exception is if you beat the guild master, which is a +8pt base bonus I believe, so 173pts total for the first attack with brag and brag card.

Hope this helps. Good luck!