Filtering (escape vs raw) Twig variable output?

Question

Twig

Record difference

{{ 'title.homepage' | trans }}
{{ 'title.homepage' | trans | raw }}
{% trans %} title.homepage {% endtrans %}

{% autoescape %}
     {{ var | trans| raw }}  
{% endautoescape %}

{% autoescape %}
    {{ var | trans }}  
{% endautoescape %}

 {% set strategy = 'html' %}
{% autoescape 'html' %}
     {{ var | trans |escape(strategy)|raw }}
 {% endautoescape %}


 {% set strategy = 'html' %}
{% autoescape 'html' %}
    {{ var | trans |escape(strategy) }}
{% endautoescape %}

Even with strategies, ugh bells and whistles.
I'm a bit confused what, when and why is it preferable to use?