Whether one or more rails are better is the subject of some disagreement. Single railers argue that with everything on one rail you don't have to worry about balancing or uneven loads. Multiple railers point out that separate rails provide more safety as a problem on one rail is isolated from components on the other rail. Take your pick.
Your PSU is very good - not top of the line but still very good - and has quite a surplus of power over the requirements of your system.