We consider nano-optical couplers that consist 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 curving the bend. In this contribution, we present a detailed investigation and analysis of coupler performances to critical geometric parameters. While the designed couplers are robust against fabrication errors, numerical results demonstrate a remarkable dependency of coupler characteristics to particle types, as well as to bending geometry, due to strong plasmonic interactions at short distances. These findings further support the need for case-dependent optimization that must be performed efficiently and accurately via full-wave simulations.