From the blog "SCRIPT INTENSIVE HEAVY??? REALLY"

The first point is about the number of scripts in a mod. Many people think that a mod with thousands of scripts is a "HEAVY INTENSIVE SCRIPT" ==> FALSE The number of scripts in a mod is NOT related to the weight of the scripts. The base game has 10k scripts, Dawnguard and Dragonborn add 3k and that does NOT mean "SCRIPT INTENSIVE HEAVY". A mod like 3DNPC has 6836 scripts and that does NOT mean "SCRIPT INTENSIVE HEAVY". A mod like slaverun has 4104 scripts and that does NOT mean "SCR