One of our Clopay engineers saw your question and wanted to respond.
1. Yes, it is normal. What it matters is the combined torque from both springs that generates sufficient power to lift the door. It doesn't have to be equal, one may contribute 40% and the other contributes 60%.
2. The length of the spring is designed to meet certain cycle life of door operation. They can be anywhere from 20" to 45" long in most of the residential applications.
If you have any further questions please feel free to call our customer service dept. at 800-225-6729 or use the live chat feature on our web site at www.clopaydoor.com