This is a quick tip and not necessarily the best way of managing multiple versions of edits but so far I find it works well.  Just like you can audition specific clips in the FCPX timeline you can also audition a group of clips and also a full edit.

Just select all the clips in your edit, press option G to make a new compound clip.  Then select ‘make duplicate for audition’ and you’ll have a new version of the compound clip that you can manipulate.  To switch between audition versions just click the the audition icon at the start of the compound clip in the timeline and select the version you want to work on.