We consider optical couplers that consists of optimal arrangements of nanoparticles to improve the transmission abilities of nanowire systems with sharp bends. Previously, it was shown that absence/existence of nanoparticles in a given grid can be optimized such that the power transmission can significantly be increased without smoothing the bend. In this contribution, we present the sensitivity of coupler performances to the particle geometries. Numerical results demonstrate a high dependency of coupler characteristics to particle types due to strong plasmonic interactions at short distances. These findings further support the need for case-dependent optimization.