If I have a 3 bay NAS how would that be configured? I understand a 2 bay system with a RAID 1 setup, I think. But what happens when there are 3 drives? And if I have a 3 bay system do I have to use 3 drives?
Three drives is the minimum for RAID 5. You can also do two drives in RAID 1. Depending on what the NAS supports you can do two or three drives in RAID 0 or JBOD. And maybe three independent volumes.
Of course you don't have to use all three drives or even install them.