OFDM signal suffers from high Peak to Average Power Ratio (PAPR). This dictates the necessity to drive the nonlinear power amplifier with high back-off, which leads to low power amplifier efficiency. In this paper we consider system that contains Iterative Clipping and Filtering (ICF) at the transmitter for PAPR reduction and modified iterative receiver (MIR) for demodulation. The MIR demodulate the distorted received signal. The distortions are created by the ICF and the nonlinear PA. The system architecture provides two main degrees of freedom given by the two back-offs: BO1 for ICF and BO2 for the power amplifier. We suggest to exploit these degrees of freedom in order to optimize the system performance expressed by a triplet: power efficiency (PE), adjacent channel power ratio (ACPR) and symbol error rate (SER). The optimal pair [BO1 BO2] depends on the priority among ACPR, SER and PE. Once the priority is determined, the optimal pair [BO1 BO2] that optimizes the system performance is found. An example of a hierarchy is given.