Theres nothing your missing out on by running a PC - midi sync isnt that crash hot no matter what system your using. For routing audio on the PC theres the choice or JackDmp and VirtualAudioCable. Lets not hijack this topic with any more pc talk though.
Yeah but you need two soundcards, then plug them into one another - one connected to one laptop, one connected to the other laptop. This tutorial is for getting them running both on the same pc which is really a much more practicle approach for the mobile musician.
When you speak about selecting something, you may want to zoom into it as it hard to see on a YouTube vid.
This I believe you have setup for total output from Traktor. You may want to show (up to you anyway) how you can send from each channel separately to use effects on those channels only.
Should be noted this isnt smartmixing - this is simplly audio routing.
Smartmixing is the use of crossband compressors to take over some of the jobs of EQing.