Widget Variations allow you to individually style a widget. Choose any available variation at Appearance → Widgets → Widget Settings
There are 56 variations: box1-2, title1-2, rounded, square, dark10-95 and light10-95; nomargintop, nomarginbottom, nomarginright, nomarginleft, nopaddingtop, nopaddingbottom, nopaddingright and nopaddingleft; flush, flushtop and flushbottom; plus standardcase, uppercase and lowercase.
Note: You can compound multiple variations together such as dark10 nomarginleft standardcase flushbottom.