[RPG] Can a warforged druid use composite plating

It doesn't say it counts as armor or natural armor or anything, so it doesn't. It's just 1 AC on top of everything else, to emphasize the sturdiness of Warforged. It should stack with everything and prohibit nothing.

To support this, note that the Warforged trait provides a bonus to AC, rather than setting it to a number, as armor is wont to do. The Tortle, another race with an armor-related ability, sets its armor class to 17 like armor usually does, and correspondingly disallows further benefits from wearing armor, further illustrating that abilities that provide bonuses to the class of worn armor (like the Warforged trait) are not armor and are intended to modify armor, while abilities that provide a different default armor class probably count as armor and definitely don't modify the effective class of worn armor.

RAW, Yes. (Although with a huge caveat of both being playtest material from different sources^)

If you have multiple features that give you different ways to calculate your AC, you choose which one to use. (PHB p. 14)

Neither of these are a new way to calculate your AC. Bonus from different sources definitely stack unless they say otherwise according to Jeremy Crawford. These are both listed as bonuses. So you would calculate your base AC and add both bonuses.

Why it might not work

Both are reliant on the specific nature of the creature's physical build. One with wood/metal, the other changing your skin to leather. It wouldn't be a stretch to suggest that altering your physical form to a bestial form changes your current form (wood/metal) to leather, replacing the original +1 to AC. There is nothing mechanically that forces this and an extra +2 to AC is not outlandish considering the other options available to increase one's AC.

^ Note on all UA material. Generally combining sources is fraught with untested balance possibilities

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