This mirrored that original design you made a choice at first level and that defined your armor moving forward. The juggernaut subrace had the equivalent of heavy armor, the skirmisher was medium, and the envoy was light. In the earliest draft of the WGtE, we mimicked this original model by tying armor type to subrace. This added a unique flavor to the race, though it did require a character to burn a feat. In that early edition a warforged character used a feat to set their armor class, and once set, they had it for the rest of their life. When the warforged were released in the original Eberron Campaign Setting, one of their defining features was that they didn’t wear armor they WERE armor.
The final version released in Rising is quite different from Wayfinder’s, and I want to discuss those changes. The warforged have gone through multiple design iterations in Eberron, from an early Unearthed Arcana article when Fifth Edition was first released to a more developed version in the Wayfinder’s Guide to Eberron. A warforged barbarian could describe their Rage as entering an advanced battle mode, while a warforged sorcerer could present themselves as a living wand. Whether you embrace it or rebel against it, you were created for a purpose and your class features may be reflected in your physical design. As a warforged you don’t eat, sleep, or breathe. Robot or not, a warforged character is quite different from other species.
Warforged have feelings, and while this is something that’s debated in Eberron itself, the fact is that they have souls the real mystery is where those souls come from. A warforged can be healed, and they can even be poisoned, though it’s not easy. Their musculature is formed from a rootlike substances, and they have a circulatory system of alchemical fluids. Warforged are formed from wood and metal, but they are living creatures. Warforged are often dismissed as “magical robots,” but it’s a flawed analogy. Sentient golems created to fight in the Last War, they must find their purpose and place in the world now that the war is over. The warforged are one of the defining elements of Eberron.