Backplates can be static, or be ruled by solvers, or be interactive in nature (grabbable), but fit with solvers to enhance the experience and discoverability. Their use and behavior depend on the type of experience the use case requires.
Touch = UIs placed at 50cm (~20 inch) from users
Backplates for touch UIs are bound to ergonomic requirements. They are sized according to the content and, if grabbable, fitted with grips ideal for touch or maximum near interactions with indirect interaction support (far interactions).