DJM 800/900 - 2 channels midi (traktor) and two channels normal audio input - Possible?

Hi,

I'm thinking about buying either a DJM 800 or 900. But the way I want to use the mixer might create problems. I'm totally new to the Pioneer family.

The way I want to use my DJM 800 or 900 (haven't decided which one yet) is to connect ONLY 2 channels of the mixer to two channels in traktor (only software). To control faders, eq and such. BUT, here is the question. Can I connect, lets say, two synthesizers to the other two available channels on the mixer? What I'm trying to say is, can I use two channels on the mixers to be midi controlled and two channels on the mixer NOT to be midi controlled? And does this work on both 800 and 900?

And also, can I choose what buttons actually are midi controlled? Lets say I want ONLY the "start fader"-buttons to control something in traktor and the rest of the mixer to me neutral?

Would appreciate an answer from someone of you.

Thanks