Hi helpyou,
As usually Ex e is used for junction boxes, as it's based on using of equipment that is less possible to induce sparks or high temperature. So all equipment installed inside the enclosure has to be Ex e certified. Also it's usually placed in Zone 2. Ex e is allowed for Zone 1 in places protected from tough weather conditions. All changes of equipment inside enclosure has to be approved by manufacturer, in order to keep certificate legitim.

Ex d enclosure has better protection, because it doesn't allow explosion to come out from inside of enclosure to outside. That's why equipment installed inside the enclosure can be non-explosive proof. It can be placed in Zones 1,2. It's heavier than Ex e, because Ex d is usually made from steel. There are some requirements to open spaces inside enclosure but as usually vendor is in charge of this calculation.

Ex d (Flame proof) - Up to Zone 1 : Usually Die cast AL/Iron. Wiring rigged in such a way that the power trips if the lid is opened. Glands have to be Ex d rated too. Max wattage of each component has to taken into account before wiring. Extensively used in lighting.

Ex e (Increased protection ) - Usually Up to Zone 2 : Only certified components inside.