Hey MangoKingllc,
The best practice for segments is to set each segment as a geo (or geo group) based segment, because active geo segments will override the Global Segment. Within these geo segments, you can vary the ecpm based on location (e.g. set higher ecpms for higher paying countries).
This allows you to set different ecpms per ad network depending on how they perform in each respective geo. It also allows allows you to target ad units with inventory from ad networks for specific Geos as well.
Let me know if you have any questions or need me to clarify anything further.
Edward
