Reply to S4 Question regarding channels C/D

I been reading old post and been doing my own research and I just need confirmation before I pull the trigger and purchase an S4.

So I plan on Purchasing the S4, but was wondering if I'll be able to connect two cdj 400 to channels C/D and be able to use each to play CDs from (NOT TIME CODE) while using Deck A/B in Traktor.
I've read that the CDJs can activate Time Code on USB Mode (I don't want this). I'm a bit confused as to what "THRU Mode actually does".

So connecting the CDJs to Channel C/D won't be the issue. My question is - When I connect the CDJs to Channels C/D on "THRU Mode", what will be the output? Will I be able to control the CDJs playing CDs on Channel C/D on an independent Channel or can I only do Time Code?

Thanks for reading, I been trying to figure it out myself, but the post I read don't quite answer my Question. If I can't play CD on the CDJs I'm going to be forced to buy a Xone 4D