I have no idea how application/invites worked. Was probably organised on the official Discord, like the last tournament?^[1] There are some good, high ranked players among the teams like Lystic and Hydration - and of course MikaelS (current top MMR player by a lot) is leading one of the teams.
It's a shame the spectator tools apparently aren't great at the moment (as expected from a closed beta game), I would have liked some good Freecam overview footage instead of player perspective only.