How to disable user and e-mail input auto-fill?
Something in the core stores user login and drupal use this information in every form submit, in other lines, I can't let user change 'user' and 'e-mail' inputs. BUT, I found how to change markup and correct my design. Follow...

In 'mytemplate'\templates\form\form-element.html.twig I changed:

...[omitted]...

78.   {{children}}

...[omitted]...


for:

{% if logged_in and element['#type'] == 'item' %}
  &lt;input type="text" name="{{name}}" value="{{element['#value']}}" disabled&gt;
{% else %}
  {{ children }}
{% endif %}


And my form now looks like this: