Entirely custom checkout page (NextJS)

We are trying to integrate Snipcart in our NextJS app. We already have our own checkout page and want to use Snipcart SDK/API to get the current cart items and display them in React. We would expect a method in the SDK/API that allows us to get the current cart items (something like Snipcart.cart.items.list()), but we can’t find a way to do it. Any ideas?

We would also like to manage the process of placing an order ourselves programmatically. Again we would expect some method that allow us to pass all the necesserary info and make an order (e.g. Snipcart.orders.create(userData, paymentData)) but it seems like the only way of placing an order is through Snipcart’s cart UI. Is there any way of doing this using our own checkout page and not customizing Snipcart’s templates?