Well I would say it depends on your business use case if your business would like to know what specific product users are adding to their cart then only send product info of product which user are adding to the cart(single event), you need to trigger an event on click of Add to Cart button on the page, the next action will depends on the UI/UX of the your website if after adding a product to cart cart page is also loading by default then you can trigger a cart view event and send all the items details available in the cart.
You can refer to the schema document for more details on eventType field.

I hope this will help.