Award ticket is treated as a revenue ticket. If you have Oneworld status, then those extra benefits like extra luggage allowance, lounges etc, would be carried forward provided your FFP is on the booking or when you show your card/membership at check in.
If you have no status, however, X class which is CX's award class, you cannot get any seat selection until you do OLCI. If you have status, you need to call CX to get your seat assigned as the website cannot do this for you.