I don't really know how it works, i tried reading http://support.microsoft.com/kb/2458544 but it really isn't that detailed, im currently using: Windows defender + firewall + smartscreen + UAC (so basically windows 8.1 default security)
EMET will considerable increase security of your config, though you can encounter some issues. In general if you successfully setup EMET and check all covered apps (just launch them, make all routine operations and close) than it works without any problems. You can start from "recommended security settings" and load "poplular software" and "recommended software" templates.