Do I have to use Stripe or Paypal? What if I prefer something different?

Stripe and PayPal are the only payment processors that you can connect to your online store. You can decide to do one or the other (or both). The only other payment method that you can enable is Apple Pay but you must first connect Stripe in order to enable this option. I recommend enabling Apple Pay if you use Stripe since it offers another fast, secure way for customers that use Apple Pay to buy from you.