malct no you do not need a CX account to either take a CX flight or credit miles from a CX flight to any other OW account

The benefits of having a CX account (which you must input the FFP# in the booking), from the top of my head, are:
- you can OLCI at T-48 instead of the T-24 available for non-members
- you can avail member-specifix promo codes, if you have them

else, depending on your fare class, you'll be fine with your QR FFP#