Speed up the checkout process by skipping the ‘Add to Cart’ step and directing users directly to the checkout page. The Magento 2 buy now button allows customers to enjoy a one-click checkout experience. This feature is particularly useful for returning customers who don’t want to add products to cart first and then move to the checkout page.
The Magento 2 Buy Now Button Extension simplifies buyer’s journey which increases conversions. A very useful feature of the extension is that store owners can choose which specific products, customer groups or store views to show 'Buy Now' button on. They can also create different 'buy Now' buttons with different calls to action.
More details here: https://www.fmeextensions.com/magento-2-buy-now-button.html