Triplex is the Dutch term for a sheet with three bonded wood layers. Multiplex is used more broadly for plywood with multiple layers. Product names do not always make a strict distinction, so the label alone does not identify the best sheet for your design.
Look at species, layers and thickness
The outer layers determine much of the appearance. The core and complete sheet construction affect weight, stiffness and edge appearance. Two sheets with the same nominal thickness can therefore feel quite different.
Birch plywood, poplar plywood and thin aircraft plywood each have their applications. Compare their product information in the plywood collection.
The layers appear in the cut edge
Laser cutting exposes the wood and adhesive layers along the edge. The edge darkens and varies between sheet types. On a small box or open construction, this can be part of the appearance. If you intend to conceal it, account for finishing when choosing material.
Designing a joint
A slot fits the actual thickness, not the product name. Test a new joint in the same species and thickness. Thin layers and fine details also require attention to direction and the width of the remaining material.
For choosing a wood species, start with the material products. For a suitable joint, read about tolerances and fit. An extra wood layer is not a quality guarantee by itself.