(See the best response by Ter13.)

Problem description:

Just curious o the different ways to ru an AI system for mobs that attack, follow, wander ad even runaway.

Whats the best and efficient way?
Best response
Make one. Bring the code here. We can give you advice on improvements.

This question is too broad to be answered.
Use 'State-based' code. Change states based on environmental checks.
Also, check out some demos. There's loads and they're easy to find.