Paypal: Orders API vs Payments API, and finding better documentation

I am completely lost among PayPal's API documentation. I have been working with the orders API and the PayPal Checkout SDK trying to set up payments for a project. In trying to decipher the Orders v2 API reference, for the use of making multiple captures towards a previously authorized total for an order, I found a bunch of what seemed to be more useful documentation discussing the Payments API instead. I'm having trouble understanding what the difference between the two are or which I should be using or for what.

The Orders API Reference says the following:

An order represents a payment between two or more parties. Use the Orders API to create, update, retrieve, authorize, and capture orders.

While the Payments API Reference says this:

Call the Payments API to authorize payments, capture authorizedpayments, refund payments that have already been captured, and showpayment information. Use the Payments API in conjunction with theOrders API. For more information, see the PayPal Checkout Overview.

They are both describing doing almost the exact same things and the Payments API says it should be used in conjunction with the Orders API without actually providing any guidance for how they should be used together. The "Checkout Overview" link given goes to the guide for Smart Buttons with the Orders API and doesn't actually ever mention the Payments API.

So my main questions are as follows:

• What is the difference between the two APIs?
• Which API do I need to use to support multiple captures? It seems like Payments is the only one which supports multiple captures but I already have infrastructure in place using only the Orders API to create an intent=AUTHORIZE transaction, have the order_id sent to the client so that PayPal can be popped up and the order authorized, and a webhook to receive the notification for that authorization. Can I now use the Payments API just to capture from that? Do I even need to? I can't find anything related to multiple captures in the Orders documentation.
• Is there any other good literature describing how all of the moving parts of the Checkout SDK and the Orders/Payments API fit together for a smaller scale project? PayPal's own guides are all over the place and do very little to describe how the different parts interact or when you need one API vs the other.