Hi!.

You only have to add options parameter, as shown below.
<field name="address_type" widget='radio' options="{'horizontal': true}"/>

Btw, in my code y used address_type as a selection (fields.Selection)

See u later.

You can use groups tag

See example below.

   <group string="Administration">
       <field name="privacy_visibility" widget="radio"/>
   </group>
   <group string="Miscellaneous" name="misc">
   </group>

Thanks,