What Mr Gulpener has written is correct and important. As a recommendation, I can add that it makes sense to replace the built-in fan with one from Noctua. Someone on the net has designed a mounting part for this and provided a template for 3D printing. This improves the cooling performance and minimises the background noise. Not a must, but if you need it, add it.

No they are not and I would recommended to get angled sata cables which will save you extra space.