The case comes with a "3 Mode" Fan control. You can choose between "full stop", "cruise (seems to be 60% speed)" and "full" speed. 20W should be enough to attach all five LED fans to the controller and it should still handle it. If that actually is the case ... I can't say, but it would make sense.
That case is a failure. If you like fancy and don't want to spent to much on the case, get a Zalman Z9 plus or Z11 plus.
If you plug the fans into that then yes, the 3fan thing will be unused, unless you add more fans in future and plug those into it,
And useless Usb ports is something I'm unfamiliar with hehe, you can always find a use for them :-)
External storage drive
I have two temp sensors running off a couple of my Usb ports, a flashdrive set for readyboost
A toolkit flashdrive that lives there till needed
And my phone cable,
No such thing as useless ports in my opinion :-)