You can add unlimited things and accounts from the cheapest package. However, subscription purchases are followed by a higher-level package which starts from $27 a month. If you are looking for the Best Ecommerce platform for small businesses then you might want to keep this in mind.
If you want to know about the payment methods, Wix offers payment methods. The options include more than 40 partners including PayPal, Stripe, and Square. They also have a Wix Payments, an in-house portal, which can be used to accept payments for credit/debit cards and connect with other providers of payment.
You also have a converter that allows you to accept foreign currency and sell your goods worldwide, starting with the unlimited plan. Wix is also equipped with a fairly useful digital sales tax calculator. This functionality, however, has limitations in the transaction count depending on your choice of plan.