Keep in mind a lot of these things could have changed and the sources are no longer viable. Except maybe Anex's because it was a planned future addition.
Things like a level 1 guild permitting 100 members may not be true. The Korean version allows for only 30 members, this will probably be changed to something more when we receive our version.
Currently I don't have much info on guilds, since when I did manage to get into a guild in the KR version, it wasn't for very long because it was on the last day of CBT.
Things that I do know:
~ There is a guild search system.
~ Guilds can list themselves to be open for recruitment on the guild search system. The system involves applying for a guild and the guild will then receive your application and can either accept or deny.
That's all I know for now that is certain. But once again, a lot might have been changed already, and a lot more can change between the KR version and ours. Although the basics will probably not change.