A modular panel unit according to one embodiment includes a major subunit adapted for being secured to a keyed backing panel, and at least one minor subunit. The major subunit includes at least one connector adapted for coupling to a corresponding connection feature of the keyed backing panel in order to secure the major subunit to the keyed backing panel; and one or more coupling features. Each minor subunit includes: one or more couplers adapted for coupling to the one or more coupling features of the major subunit in order to secure the minor subunit to the major subunit. Additional systems and methods are also disclosed.