Adding Monobehaviours to Pure ECS Entities/Archetypes?

Can I add Monobehavoiur Components like Transforms, Animators and Stuff to Entities/Archetypes (since they have to be declared in code)? Or should I go the GameObjectEntity route and use ComponentSystem for Monobehaviour Context and IComponentData/JobComponentSystem for "pure" ECS? (Which I guess is just Hybrid ECS, even If I use JobCOmponentSystem)

Can/Should I still use EntityManager and World/Archetypes then?

 

You can use EntityManager.AddComponentObject to add Hybrid Components to an entity.