Organic electrochemical transistors are considered today as a key technology to interact with a biological medium through their intrinsic ionic-electronic coupling. In this paper, the authors show how this coupling can be finely tuned (in operando) post-microfabrication via the electropolymerization technique. This strategy exploits the concept of adaptive sensing where both transconductance and impedance are tunable and can be modified on-demand to match different sensing requirements. Material investigation through Raman spectroscopy, atomic force microscopy, and scanning electron microscopy reveals that electropolymerization can lead to a fine control of poly(3,4-ethylenedioxythiophene) (PEDOT) microdomains organization, which directly affects the iono-electronic properties of organic electrochemical transistors (OECTs). They further highlight how volumetric capacitance and effective mobility of PEDOT:polystyrene sulfonate influence distinctively the transconductance and impedance of OECTs. This approach shows to improve the transconductance by 150% while reducing their variability by 60% in comparison with standard spin-coated OECTs. Finally, they show how the technique can influence voltage spike rate hardware classification with direct interest in bio-signals sorting applications.