I assume the no alt clause means I can't join with two accounts, not that people care what account I join with?
Yes. That's correct. If I suspect you are an unknown alt, I will PM you, over your identity.
What do you do if there are more people who sign up to play in the league than the amount needed to make the tournaments?
I expect to have more sign-ups than slots. We need that to give the managers some room to operate with. Not everyone will get the amount of games they sign up for. If a really large number of players do not get to play, I will consider increasing the size of the league in terms of more clubs/ more divisions(promo/relegation system)/ more formats to play per club etc.
I would like the first season to be a short format, so that we can learn from it and perfect the system.