A question came up on today's Champion Webinar to move the values of a Radio Button or Checkbox field to another Radio Button or Checkbox field later in the form.  Here is the JS for Modern Designer to do this:

LFForm.onFieldChange(function() {
  var value = LFForm.getFieldValues({ fieldId: YOUR FIELD ID });
  LFForm.setFieldValues({ fieldId: YOUR FIELD ID RECEIVING VALUE }, value);
}, { fieldId: YOUR FIELD ID });

If you want to make the second field Read Only to force a match you can either use Show/Hide fields to disable the field when its not blank or use this script:

LFForm.onFieldChange(function() {
  var value = LFForm.getFieldValues({ fieldId: YOUR FIELD ID });
  LFForm.enableFields({ fieldId: YOUR FIELD ID RECEIVING VALUE }).then(function() {
    LFForm.setFieldValues({ fieldId: YOUR FIELD ID RECEIVING VALUE  }, value).then(function() {
      LFForm.disableFields({ fieldId: YOUR FIELD ID RECEIVING VALUE  });
    });
  });
}, { fieldId: YOUR FIELD ID });