Use require registration -- "guest" accounts have historically been implemented, but due to protocol limitations they are essentially throwaway "real" accounts, and suffer from the negative consequences of this [https://vtluug.org/w/index.php?title=Matrix&action=submit#Issues_with_the_Matrix_Protocol|detailed below].

A "Matrix room" is the equivalent of an IRC channel. A "Space" is the semantic equivalent to a Discord Server or Slack Workspace. Confusingly, a user doesn't need to be in a Space to chat in one of the rooms within. On top of this, rooms don't need to be contained within a Space.