Non-refundable means you cannot get a refund to the original form of payment.
Non-changeable means "use it or lose it" which is only the case for Basic Economy fares (possibly with exceptions for a fee).
Otherwise, all main cabin/first class tickets are changeable - pre-pandemic you would have to pay $200 to change it, now there is no charge. Effectively, you get a voucher for the full value of the ticket, although it can only be used by the same passenger.