The spin qubit community explores various semiconductor heterostructures and gate designs to build a fault-tolerant quantum computer. Characterizing semiconductor heterostructure experimentally is a demanding task, with the full development cycle taking at least months of work. While numerical simulations are more time-efficient, their predictive power is limited due to unavoidable disorder and device variations. In the current work, we develop a spin-qubit device simulation that predicts the coupling strengths between the electrostatic gate potentials and the effective device Hamiltonian. By comparing our simulation results with the experimental data, we demonstrate that the gate couplings to the dot chemical potential and the interdot tunnel coupling are correctly predicted even in presence of disorder. To demonstrate the flexibility of our approach, we also analyze an alternative non-planar geometry inspired by FinFET devices.