Our research aims to provide a comprehensive understanding of XPaO3 (X = Cs, Rb) compounds, employing density functional theory as a guiding tool. Through the examination of their structural, electronic, elastic, and optical properties, we offer valuable insights into their versatility and potential in emerging technologies. This study strives to make complex materials more accessible, paving the way for their application in practical and innovative contexts. We commence our investigation by studying the structural aspects of XPaO3 (X = Cs, Rb) while using Birch-Murnaghan fitting. We endeavor to reveal the underlying crystal structures, lattice parameters, and overall stability, providing a fundamental understanding of their composition and behavior. Continuing into the electronic realm, we delve into the band structures, electronic density of states, and charge transfer properties of these compounds by using the recommended modified Becke–Johnson potential. This facet of our research sheds light on how they behave in electronic applications, offering insights into their suitability for emerging technologies. Our study also undertakes the mechanical properties of XPaO3 materials, including elastic constants, bulk modulus, and shear modulus utilizing the IRelast package. These mechanical characteristics are pivotal in determining their resilience and suitability for a wide range of practical applications. Lastly, we explore the optical properties of XPaO3 (X = Cs, Rb) by calculating parameters such as dielectric functions, refractive indices, and absorption coefficients. These optical insights hold promise for potential use in optoelectronics, where materials interact with light to power various devices.