Abstract: The Rayleigh-Taylor instability (RTI) is ubiquitous in many fluid flows, such as astrophysical plasma flows. The RTI encourages mixing in a medium with an unstably stratified density profile under the influence of an accelerating force such as gravity. If a sheared magnetic field profile is present, the RTI can cause reconnection to occur through plasma mixing, leading to nonthermal particle acceleration for sufficiently low beta plasmas. While the kinetic effects of this phenomenon have been previously studied in two-dimensional simulations (V. Zhdankin, B. Ripperda, A. A. Philippov, 2023), three-dimensional effects have not been explored. Here, we directly compare two-dimensional and three-dimensional localized particle-in-cell kinetic simulations to elucidate three-dimensional effects on RTI-driven magnetic reconnection in a sub-relativistic pair-plasma subjected to a sheared magnetic field profile and RTI-unstable density stratification. This analysis is carried out for a parameter scan across magnetic shear angle values. We expect that these results can provide further insights into plasma physics governing reconnection as well as the near-infrared and X-ray flares observed from localized regions of the accretion disk surrounding Sagittarius A*.