RuntimeException: Operating in TEST mode but no test mode email has been set yet. Aborting send. in Drupal\commerce_abandoned_carts\AbandonedCarts->queueSendMails()

On the Commerce Abandoned Carts settings you can figure a test mail address. Or you can disable test mode. Do one of these and that should resolve this issue.

If it doesn't resolve your issue, feel free to reopen this issue.

Is there a config variable I can add to my settings.php for each option?

Yes, this is possible for all config.

Example for overriding configuration for Commerce Abandoned Carts in settings.php:

$config['commerce_abandoned_carts.settings']['testmode'] = TRUE;
$config['commerce_abandoned_carts.settings']['testmode_email'] = 'foo@example.com';

Automatically closed - issue fixed for 2 weeks with no activity.