For what i know, Cubase does not create REAL 32 bit files unless there where any process. By process, i mean a simple fader change in the mix, a pan, or a virtual instrument or eq. So you should export all files with everything bypassed. Preferable you should use an external audio editing software since i don't know if you have that kind of control with Cubase.
As far as i know, if manage to do so, cubase will only truncate and even if you don't dither (you should always dither when you truncate digital files with content - i.e. 24 to 16 bit) you will not truncate significant information. In this situation i wouldn't use dither.
Last edited by mcatalao; 2013-09-27 at 17:20.