The presentation will focus on the interplay between structural, interfacial and optoelectronic properties in 2D multilayered halide perovskites, either in Ruddlesden Popper (RP) or Dion Jacobson (DJ) structure. At present, perovskite materials are mixed with each other in complex alloys and heterostructures, including 2D/3D compositions, combined with additives or protecting layers to improve their stability and/or defectiveness as well as assembled with carrier selective layers, other materials and components to turn them into devices. Considering the target applications, ambient conditions predominate with additional issues related, for example, to the intrinsic dynamics in action in the MHP structure that may not be well captured using static averaged structures. Based on a set of customized examples, this talk will summarize recent theoretical results obtained by our group that aimed at answering questions such as: i) How do these engineering strategies impact the work function and absolute valence band energy of the MHP material? ii) Is it correlated with surface/interface dipoles? iii) Can one quantitatively assess energy level alignments of MHP semiconductors based on first-principles electronic structure calculations? How can one get rid of the stochastic dynamics of organic cations and further include cation and anion alloying while computing materials properties? iv) Is it possible to extract semi-empirical formula for molecular passivation at surface or transitivity rules for interface dipoles? Special attention will be paid on newly discovered phases and compositions and opportunities to further engineer MHP properties in connection with their use in devices under working conditions. We will see that in practical cases the funneling of electronic carriers to the 2D crystal edges, important for ionization of electron-hole pairs in 2D RP phases, is also at work in bromide perovskites. Continuous and ultrafast photodoping will be further discussed, demonstrating their strong impact on the structural and carrier transport properties of DJ perovskites