3 quick questions in regards to controller

[m_c]

1) EMC filter. Helps stop noise escaping from the control box into the mains supply, and also stops noise coming into the control box from the mains.
2) It's a bit tight, but I've see far tighter. Just keep an eye on temps.
3) 24V is pretty low for steppers, and will limit your max speeds. I'd personally aim for at least 36V, but you can always upgrade later, as it's easily swapped.