If you choose to subscribe to Airtame after the trial ends, you will regain access to the licensed features based on the Airtame plan you select.
All paid settings you have enabled and defined during a trial are saved on the device as will revert back upon applying a paid license. For example if you implement a playlist with custom digital signage, this playlist will stop showing when the trial expires. But upon applying a license to the device, the playlist will automatically start showing again.