In this study, we demonstrate a well-established strategy for controlling the threshold voltage (Vth) in organic thin-film transistors (OTFTs) by applying uniform gold nanoparticle (AuNP) coatings onto silver nanowire (AgNW) electrodes using a galvanic replacement process in the presence of NaCl. This approach highlights the potential for low-energy consumption operation. The AuNP coatings effectively adjust the work function of the AgNW electrodes to better match that of the organic semiconductor. As a result, the OTFT devices show significantly reduced threshold voltages, enhancing charge injection efficiency and lowering the operating voltage. Additionally, when used as synaptic transistors, the optimized Aucoated AgNW composite electrodes demonstrate superior neuromorphic performance, including a lower maximum drain voltage (VDS), indicating a potential for improved energy efficiency per spike event. This advancement marks a critical step toward developing low-power neuromorphic devices and low-voltage flexible electronics. Our work establishes a practical methodology for quantitatively and reproducibly controlling Vth through precise modulation of metal coating uniformity, providing a solid technological foundation for future optimization of organic electronic devices.