Will a paypal button appear on form while in edit mode or after publish?

No, when you Integrate your form with PayPal only the products would be seen in your form and only the submit button would be seen in your form.

Here is a sample screenshot of a  Paypal form:

However, you can change the submit buttons image into a PayPal button.

Here is a sample URL  to be used in your submit image.

https://www.paypal.com/en_US/i/btn/btn_dg_pay_w_paypal.gif

Sample:

Hope this information helps.

If you have further questions,please let us know.