In this WordPress PayPal + Stripe form example, you can let the user choose the payment method. In order to do so, you have to have the Payment element present in your form. Depending on the options values in the Payment element, the plugin will automatically route the user to the checkout page or dialog.
Option values should look like this:
The values paypal and stripe are necessary to route the user to the relevant checkout page / dialog, respectively. All other option values will be “ignored” and the form will be submitted regularly.