dual overflows are no big deal; you can run two pieces of flexible tubing into a Y and then into your sump or you can run both direct to the sump, or you can hard plumb directly into the sump or into a Y and then into a sump. Its really just about how much work you want to do. Plumbing freshwater is something I've personally never done, but I've seen picture of some done on here. Megoosh had one he did on his 30 that looked like a pretty cool set-up.
One problem with the built in overflows, as already pointed out, is that the tank has to be full in order for them to work.
"Listen to some of these guys talk, and it's like they were born from their momma's belly with a fishkeeping encyclopedia in one hand and an API kit in the other" (unrevealed).