BrevWoo

Brevo (formerly Sendinblue) is a marketing automation platform. This plugin adds customers to Brevo when they purchase your WooCommerce products.

From the "SMTP & API" section of your Brevo account settings, in the "API Keys" tab. It's recommended to create a new API key for this plugin e.g. you could label it "BrevWoo". Once you have an API key, enter it in the plugin settings at Settings > BrevWoo. View the official Brevo documentation for more information.

Yes. You can select any number of default lists in the plugin settings, and also select any number of product-specific lists in each edit product page.

Yes, the plugin uses the list ID, not the list name, so renaming a list in Brevo will not affect the plugin.

Yes, Brevo has an official WooCommerce plugin as well as a main plugin. BrevWoo is a complimentary plugin that provides a simple set of features including adding customers to product-specific lists. You may or may not need any of the three plugins, check the features of each to see which best suits your needs. Having BrevWoo installed alongside the official Brevo plugins should not cause any conflicts.