Not addressing all questions as you'll find many answers in the FAQs/existing threads.
You can mount the "pc" case where ever you want provided there's sufficient space for it and adequate room to cool.
Personally I'd recomend using a carpc with and external optical drive. This will give you much greater freedom as to where to locate the "pc". Slot loading drives definetly intergrate better from a looks perspective when console mounted, so i'd research this option.