The plugin is GDPR compliant. You can read about which options have been added to make it compliant.
Among the plugin options in YITH > Abandoned Cart > Settings, you can choose whether saving the abandoned carts of guest users. Specifically, you can add a checkbox that the guest user has to check if he/she agrees on his email being used by the plugin.
The text of the checkbox can be customized, as well as the time that makes a cart be considered as ‘abandoned‘. If you choose that the cart has to be left unused for 2 weeks before it’s deemed as abandoned, you’ll just have to update your policies and include this time there.
Moreover, if a user wants to get his/her data deleted from your store, the plugin uses the WordPress built-in feature, so you can use that one and also the user data related to his/her abandoned carts will be removed.