Best overflow plumbing for a reef ready 120

[smokinreefer]

So with a 120,

I'd use 2 holes for return lines, 1 on each overflow.
1 drain on 1 overflow As an emergency line.

The other drain on other overflow will have gate valve.
This would be the only "working" drain? Is that right?
Unless of course something gets clogged,
then water would rise and go down the emergency line.

Would it be better to have one gated drain and one emergency drain in each overflow? And just run the returns over the top of the tank.
(Not using any holes for returns)