Details on the Amazon partnership are scarce right now, but if you’ve got a US Venmo account, PayPal says you’ll be able to use it to make purchases at both Amazon’s website and its mobile app starting in 2022, and you’ll be able to use either your Venmo balance or a linked bank account to pay.
On PayPal’s Q3 earnings call, the company stated that while the PayPal portion is still larger than Venmo, the Venmo business has now grown as large as the entire PayPal US footprint.
https://www.theverge.com/2021/11/8/22770949/amazon-venmo-us-purchases-2022-not-paypal