Let’s start with a bit of acoustics. The SB acts as a means to transfer string vibration to the air in the box which in turn acts as an acoustic amplifier much like the body of a guitar or kettle drum. So the main question is whether the shape of the box is effective. Too deep for the SB’s thickness and volume will not be as strong. Too narrow and you may get unwanted echoing. I think you can be fairly sure that a competent maker has experimented with both.

The argument has often been made that a solid wood SB of some strong elastic species (spruce, cypress, red wood, cedar, etc.) will be “better” than a high density laminate one such as found on harps such as the Ravennas, Musicmakers, Marini, etc.) because “vibrations travel along the wood grains.” true enough but for smaller harps I don’t think that makes much difference unless it is quite wide. Some may disagree with that opinion and more power to them.

All of that is a round about way of saying that if you want a small portable “packable” harp the main question is the size of your suitcase!