*"is does the .cr2s etc not make a difference overhead wise?"

*Not in any Poser vocabulary that I know of, where Posermatics are what I've paid to own Poser for.

*" used to export out background figures to bring in as props in my renders, does that not make sense memory use wise?"

*Absolutely, you're segmenting(divding the job into seperate smaller chunks,) I've always supported compositing in external 2D applications!