Paypal is my payment option but can I include a "submit order" button as well?

I'd like to provide customers with option to have an email sent to me with details of their order, so that I can invoice them via email. 

Also- does paypal widget allow them to see a subtotal and/or print an order prior to paying? I don't see that option for that when I test it out. 

I presume you would like to offer your customers to choose a payment method? If so, you can do that by following this guide: https://www.jotform.com/help/182-How-to-Create-a-Basic-Multiple-Payment-form.

With the other question you have, when you use a PayPal as a payment integration, the user is redirected to the PayPal payment gateway where they can review their order and amount before actually paying, you can test it out.

If you want to have something like a summary page before actually submitting, then you can try adding the Preview Before Submit widget on your form. 

I hope that helps.