Install only one file. This uses both the time of day AND light levels to decide if the effect should be applied.

This is the version I personally use.

Install only one file. This uses the time of day (between 5AM and 7PM) to decide if the effect should be applied.

Install only one file. This version affects only the NPC vampires taking into consideration both time of day and light levels.

Install one or the other. This version affects both the NPC and player vampires.