When I add a Feature Box, in the General Tab it says below the setting for Title Margain Bottom:
COM_SPPAGEBUILDER_ADDON_FEATURE_BOX_TITLE_URL
COM_SPPAGEBUILDER_ADDON_FEATURE_BOX_TITLE_URL_DESC
If you try and change the layout type it has the option for Icon or COM_SPPAGEBUILDER_ADDON_FEATURE_BOX_LAYOUT_TYPE_IMAGE
This is using SP Page Builder 3.7.15