I downloaded the mod recently and was testing it, but I couldn't find any option for the NPC to respawn after dying. I don't know if it's there and I can't find it but I would like an option so that the NPC could respawn after dying.

Please see: https://github.com/MarkusBordihn/BOs-Easy-NPC/wiki/Spawner which allows you to re-spawn an NPC.

This makes also sure that the NPC de-spawns automatically if it leaves a specific area and not live forever and consume uneeded resources.