In a companion article (Varady and Fedorov Ind. Eng. Chem. Res. 2011, DOI: 10.1021/ie200563e), the concept of a direct droplet impingement reactor (DDIR) was introduced as a promising approach to liquid fuel reformation for distributed hydrogen generation. Considering the overall device as an array of unit cells enabled simplified modeling of the device on a unit-cell basis. In this study, the unit-cell model is utilized to study the effects of the important reactor operating parameters for the specific case of methanol steam reforming. The performance of the baseline DDIR is compared to the ideal limit of an isothermal plug-flow reactor (PFR). The effects of DDIR shape, size, heat input and location, and droplet initial conditions were varied from the baseline design to identify possible performance improvements. It was found that the selectivity displays a distinct maximum at a Peclet number (Pe) of similar to 3 because of the interplay between back-diffusion of the products and thermal resistance of the catalyst bed. The spatial heating distribution also plays a key role, where an optimized matching of the heat input locations to the areas of heat consumption due to liquid vaporization and endothermic reaction results in an improved reactor performance, albeit at the penalty of a more complex reactor design and increased cost. Impingement of the droplet stream on the catalyst interface is necessary for proper operation, which requires certain initial droplet conditions to be satisfied, as expressed in the form of an operating regime map. Although the results are presented only for methanol steam reforming, the DDIR model is comprehensive and sufficiently general in terms of incorporated physical phenomena that it should be useful for developing similar operating criteria for other fuels and reactions requiring vaporization of a liquid feed followed by reaction over a fixed catalyst bed.