Abstract: Variability in valley-orbit state splittings will be a problem for large-scale implementations of silicon-based quantum processors. Depending on the particular qubit architecture, the role of valley-orbit states varies; however, a common theme for nearly all silicon-based qubits is that valley-orbit splittings must be precisely engineered or have large in situ tunability. Here, we investigate overlapping aluminum-gate devices for valley-orbit based qubits in Si/SiGe which enable high in situ tunability of valley-orbit states. Spectroscopic measurements of low-lying one- and two-electron valley-orbit states are taken to determine the quantitative relationship between the valley, singlet-triplet and orbital splittings. By exploiting the dependence of valley-orbit state splittings on electrostatic confinement and electron number, we show progress towards single-shot readout in the (4,1)-(3,2) electron regime, allowing for in situ tunability of the qubit frequency and enhancement of the readout window.