This is a basic question. In Electrical engineering, several designs with respect to selection of components(breakers, wire guages, transformer sizing etc) follow a set of calculated rules.
Do similar rule sets exists for power electronics, which gives clear guidance for choice of enclosures, connectors, wire guages, component ratings etc.
wire gauge --> trace width and thickness
connectors --> voltage, current, as usual
component ratings --> all as usual
enclosure --> size, isolation, stability, ... all as usual