in the Classic mode when you mix fieldset with non fieldset the fieldset are completed misaligned.
You can easily test in the sencha documentation for classic mode.
This is the modified example in the live test for Ext.form.FieldSet
Ext.create('Ext.form.Panel', {
title: 'Simple Form with FieldSets',
labelWidth: 75, // label settings here cascade unless overridden
url: 'save-form.php',
frame: true,
bodyStyle: 'padding:5px 5px 0',
width: 550,
renderTo: Ext.getBody(),
layout: 'form', // arrange fieldsets side by side
items: [{
// Fieldset in Column 1 - collapsible via toggle button
xtype:'fieldset',
columnWidth: 0.5,
title: 'Fieldset 1',
collapsible: true,
defaultType: 'textfield',
defaults: {anchor: '100%'},
layout: 'anchor',
items :[{
fieldLabel: 'Field 1',
name: 'field1'
}, {
fieldLabel: 'Field 2',
name: 'field2'
}]
},
{ xtype: 'textfield', fieldLabel: 'A test', name: 'field3'}, // LINE ADDED *******************
{
// Fieldset in Column 2 - collapsible via checkbox, collapsed by default, contains a panel
xtype:'fieldset',
title: 'Show Panel', // title or checkboxToggle creates fieldset header
columnWidth: 0.5,
checkboxToggle: true,
collapsed: true, // fieldset initially collapsed
layout:'anchor',
items :[{
xtype: 'panel',
anchor: '100%',
title: 'Panel inside a fieldset',
frame: true,
height: 52
}]
}]
});
here is the result of running the above codeScreen Shot 2017-11-09 at 2.04.54 PM.jpg

as you can see the fieldset are reduced to the label area
Thanks