You don't need to use containers, they just make life easier :)
And yes, you should only add objects that live and die together. So that wearable sprite should not be in the container.
One container can hold only one instance of each object. So you can't add CarBody and 4x instances of CarWheel into the container, it will not work.
Very common example is to add an enemy sprite and health bar to the same container. You don't need to worry about creating/destroying the health bar, nor about picking it. You can make simple events like On bullet hit enemy -> Enemy subtract 5 from health, HealthBar set width to Enemy.Health
(this enemy's HealthBar will be picked automatically)