Body class padding top, where is it coming from
It is being done by the core toolbar module. See updateToolbarHeight in  core/modules/toolbar/js/views/ToolbarVisualView.js.

updateToolbarHeight: function updateToolbarHeight() {
  var toolbarTabOuterHeight = $('#toolbar-bar').find('.toolbar-tab').outerHeight() || 0;
  var toolbarTrayHorizontalOuterHeight = $('.is-active.toolbar-tray-horizontal').outerHeight() || 0;
  this.model.set('height', toolbarTabOuterHeight + toolbarTrayHorizontalOuterHeight);

  $('body').css({
    'padding-top': this.model.get('height')
  });

  this.triggerDisplace();
},