1. During the coming competition, would there be some web page containing a scoreboard, logs, URLs to visualizers of running games, etc?
Links to visualizers and logs will all be on the Tournament Scheduler front page once the competition starts. At that time, there should be a tournament page that shows standings per game. I don't know whether it's computing and displaying the z-scores yet. Govert would know that.
2. What would be the correct way to change/update broker executables during a competition?
Unless your broker is crashing, you are not supposed to do that. Since this is a demo, you might be forgiven if you do, although Wolf might have a different opinion.
If you really need to change, get the new one ready, kill the old one while it's not in a game, and start the new one with an appropriate repeat-count. An agent is only tied to a specific simulation host for the duration of a single game; the Tournament Scheduler makes the assignment when it has a game ready. The TS and server will wait for logins for a minute or two if an agent is not ready immediately, but if you delay too long the game will proceed without you. If it's not waiting for you, then there should be no problem switching.