Which HP all-in-one systems offer a modular design with the ability to mount the I/O...

The HP Engage One Pro and HP Engage One offer a modular design with the ability to mount the I/O hub under the counter, enabling a "clean counter" implementation. This design feature is particularly beneficial for retail environments where maintaining a tidy and uncluttered workspace is crucial. The modularity of these systems allows for flexible placement of components and peripherals, contributing to a streamlined and efficient checkout or service area. These systems also provide various mounting options and configurations to suit different retail setups. References for these features can be found in the product datasheets and technical documentation for the HP Engage One Pro and HP Engage One systems.