I would like to transplant a few plants that didn't quite seem to like
their spot this season, including a butterfly bush and a salivia or
two. When should I transplant them? Now, so they can develop a root
system over the winter, or in the spring?

If now, should I cut the butterfly bush all the way back?

I'm in Zone 9 where we typically don't dip down to freezing until
January or so.

-F