Where can I find information not about the Lobby but about the game?

For information about the game in general, e.g. strategiy, adjacency bonus, tech levels, strategic icons, controls or a guide to creating a map visit an old wiki about the vanilla Supreme Commander here: http://supcom.wikia.com/wiki/Main_Page

There is a newer and almost comprehensive guide for Forged Alliance (but with outdated numbers as well): http://supcomfaguide.uw.hu/index.html

For an extensive amount of information with the latest numbers about all units in Supreme Commander Forged Alliance visit the UnitDB: http://www.faforever.com/faf/unitsDB/