Since you log in using an email address and password, you can use the same humy account after changing devices. Simply log in on your new device using your registered email address and password.
If you are logging in with a verification email, you will still be able to log in to the same humy account after changing devices, as long as you have access to your registered email address.
Since payment methods are tied to your OS (Android or iOS), you will need to cancel your Premium plan and resubscribe if your new device uses a different OS.
See here for important points to consider when changing your payment method.