Hi,

1. Here is the custom code to change your option fonts there:

   label.form-builder-radio-label {
   font-size: 15px;
   }

2. You can use smaller font size for your smaller device screens. Here is a sample code for you:

   @media (max-width: 1024px){
   .sppb-form-control option {
    font-size: 10px;
   }
   }

   You can play with the max-width value and font size value as per your need.

Note: Path towards custom CSS: Extensions>Templates>Styles> Click on your current default template name then choose Template Options. Then find custom CSS within the custom code.

Best Regards