SEE: https://calderaforms.com/doc/ensuring-caldera-forms-paypal-add-can-accept-credit-cards/

cf-paypal-customization.php

<?php
/**
 Plugin Name: Caldera Forms PayPal Customization
 */
add_filter( 'cf_paypal_request', function( $request ){
	$request['SOLUTIONTYPE'] = 'Sole';
	$request['LANDINGPAGE'] = 'Billing';
	return $request;
});