Best way to apply character effects to many enemies?

I want to apply effects to a decent size number of enemies, like burning, slowed down, poison, and I worry about performance.

At the moment I am creating this using a different particle system for each effect tied to the prefab of the enemy, so one enemy will have one or N particle systems.

- What would be the best approach to generate the same effect on several enemies (not all of them share the same model)?

- How many particles systems are too many?

- Should I attach the particle system to the prefab model or attach a particle system to the enemy object when the effect triggers?

At the moment I am not worried about the number of particles since I am trying to recreate the effect with the lowest ammount of particles possible, however, I worry about scalability and the overhead of instantiating so many particle systems.

Thanks for your time ; )