The fastest way to get a CX interview would be through their web application. The option through CTC is only for those who already have completed AQC and are already in the hold pool (or at leat that is what I was told). So, if you haven't applied with CTC yet, or have but haven't attended the assessment day or AQC, and you're interested in the CX SO position apply with them directly. You'll save a lot of time and money.