Unfortunately the consent SDK doesn't actually store if the "ad free" option has been chosen. While we could pass through through the response immediately after the user has chosen "ad free" we can't pass through that value on subsequent runs. Additionally there is a slight frustration that you cannot display the dialog outside of the EEA, I filed a request with the Admob team quite some time ago about this but they haven't responded. So if you wanted to offer an "ad free" option outside the EEA you would need a separate flow. Which is frustrating, the option is mostly exposed because the SDK offers it...
But if you did want to use it I would say the best route would be to initially check if the user has paid for ad free, or whatever restriction you've decided on. If they haven't check what the user personalisation state is. This should be loaded before the runtime starts, so the only ways it could be "UNKNOWN" are if the user consent hasn't ever been shown or if Ad free was selected. So show the user consent dialog, once it's completed the "Configuration complete" condition will trigger. If the value is still "UNKNOWN" then they chose the "ad free" option.