Recent experiments of thin films flowing down a vertical fiber with varying nozzle diameters present a wealth of new dynamics that illustrate the need for more advanced theory. Determining the regime transitions from absolute (Rayleigh- Plateau) instability is useful in the design of heat and mass exchangers for applications that include cooling systems and desalination. We present a detailed analysis using a full lubrication model that includes slip boundary conditions, nonlinear curvature terms, and a film stabilization term. This study brings to focus the presence of a stable liquid layer playing an important role in the full dynamics. We propose a combination of these physical effects to explain the observed velocity and stability of traveling droplets in the experiments and their transition to isolated droplets. When thermal gradients are present, it can induce bead coalescence away from the nozzle. To account for this, we incorporate spatial-dependent viscosity and surface tension to the model, due to inhomogeneous temperature field along the fiber.