To edit the padding click the dark grey area the adjust the padding on each
To edit the margin click directly below the text and darker grey area the adjust the margin on each
To edit the radius you need to be in design mode and select the container boxes above the solid one, change each radius accordingly.The Grey boxes are a visual representation only and shouldn't be edited.
Fixes for column margins and widths you can still set row layout options
Click the appropriate text then user the stack at the bottom to select the container.