Radiative heat transfer between an assembly of water droplets in air and a remote heat sink or source (e.g., cloud tops to higher cooler layers or solar irradiation) and associated mass transport is modeled, including droplet-vapor conduction, vapor-phase mass transfer, and liquid-vapor phase change. Two approaches for droplet sub-modeling are compared. The first approach is classical Spalding selfsimilarity theory, which is non-linear, but implicit, and easily applied to non-dilute (in water vapor) saturated states and states far from saturation. This is the approach commonly used in engineering analysis. The second approach is linearized, explicit near saturation-state theory that is commonly used in atmospheric science research and practice. Both sub-models are based on traditional fundamental assumptions but with some new refinements and adaptations in the latter to make the analysis more accurate and applicable in a wider environmental parameter space. Specifically, theoretical improvements are included in the explicit model to make it more accurate in the non-dilute regime. Clarifications of inconsistent parameter definitions are also made. In particular, the explicit, linearized sub-model's saturation-state temperature sensitivity parameter, which has appeared in the literature with conflicting definitions, is considered. Through comparison with non-linear, implicit calculations, a preferred definition for this parameter is recommended. Classical assumptions are made, which have been shown to be valid in cloud applications, including continuum vapor transport (e.g., Fickian diffusion, mass-fraction form) and quasi-steady droplet energy. The dilute or low mass-transfer-rate regime is considered primarily but not exclusively. The dilute assumption is relaxed, when necessary, to include high mass-transfer-rate or non-dilute effects via Spalding's self-similarity theory. Implications are discussed for modeling cloud microphysics, both with respect to liquid droplets overcoming the condensation-coalescence barrier in "warm" (non-freezing) clouds and with respect to droplets freezing in "cold" clouds, both of which are topics of current importance and interest in atmospheric science.