We present an analytical and numerical study of optical parametric amplification in coupled waveguides amplifiers accounting for presence of losses and spatially dependent coupling. Spatially dependent coupling enables to compensate for mismatch dynamically arising from pump attenuation and to achieve improved performances in terms of bandwidth and bandwidth-gain product compared to standard single-waveguide solutions. Our results suggest the effective design of a novel class of parametric amplifiers and could be especially relevant for integrated silicon nitride devices.