I thought bouncing was necessary in both V Vocal and Melodyne, in order to fully render the changes, so the result is the highest possible quality. If not bounced, I thought I was only listening to a lower quality preview to be used in editing until ready to bounce.

 
It will be rendered when you export the project and melodyne will use the algorithm you choose. If you select the higher quality setting, then it will export with that setting. Nothing is lost if you do not bounce first, unless you have it set up that way.
 
CJ

I used Melodyne on multiple vocal clips in a project that was vocal-heavy.  I began getting quite a bit of clicking/popping during playback, even with my buffer set to max stability,until I bounced several to clips.  I'm sure it depends on how much the rest of your project is using resources as well.