I'm not familiar with those terms or styles as this will be my first custom build. So essentially the third drain is an emergency backup drain?
If you're learning about overflow styles, check out http://gmacreef.com/aquarium-overflows-durso-herbie-and-bean-setups/
I referenced this site a lot when I was building my first tank and custom sump.

This will be my first cabinet build using 3/4” ply and no 2x4s!

