Is the DLD fee only 2% for off-plan property?

No, this is a common myth. The DLD registration fee is 4% for both ready and off-plan purchases. What happens is developers sometimes run time-limited 'DLD waiver' promotions covering 50-100% of the 4% as a sales incentive at selected launches. That is the developer absorbing the fee, not a lower government rate, so read the offer terms carefully.