You can use class :
layout : 'vbox',
class : 'buttonPadding',
Define class in your css:
.buttonPadding{
padding: 2px; //as per requirement
}
Or
You can directly use style:
layout: 'vbox',
style: 'padding:2px',
And
I am not sure but I think for:
$sheet-button-spacing and $sheet-padding
this is in scss so you need to change in scss file.
But if you change in scss file, it will reflect to all button present on sheet.
Hope it will help you!!!