5G networks are expected to support various applications with diverse requirements in terms of latency, data rates and traffic volume. Because of this, the selection of the appropriate functional split still remains a challenging task, since a number of parameters have to be considered in order to make such a decision. In this paper, we explore two possible solutions. We propose a Mixed Integer Quadratically Constrained Programming (MIQCP) model for the efficient placement of Virtualized Network Function (VNF) chains in future 5G systems, with particular emphasis on different aspects of the functional split between the cloud platform and the radio access points. Then, we also express the placement problem as MaxSAT instance and provide formal assurance of policies by considering increasingly relevant scenarios where the radio access network (RAN) needs to support various slices. Hence, thorough analyses are performed and recommendation for split point between central cloud and distributed radio units are discussed in this paper.