Sure, you raised interesting points.( a.) That would be nice to have communty founders decide the type of community, which will indicate the features that are possible in each.
B. Whitelisting will solve a lot of headache at sources as against using crowd action through downvoting to deal with spammers
About... whitelisting. Currently there isn't this possibility. But there is the possibility of blacklisting. Muting either one post or the author. This is of course not ideal, that's why most likely if one prefers whitelisted authors (or authors and commenters), they will wait for the respective type of community to be introduced, as I described above.