I was think of my next character being a Warforged and I got to thinking does the feats related to wearing a certain type of armor interact with their integrated armor.

I believe so. I asked the same thing about Heavy Armor Master and the Heavy Armor plating and the consensus was that it counts. Under the Racial description Integrated Protection Mode it says that the lightest version in Unarmored and the other two Armored. Their armor ratings (medium and Heavy) are comparable to normal Medium and Heavy armor.

Personally I'd say it's not possible. The integrated armor feature specifically states:

Integrated Protection

Your body has built-in defensive layers, which determine your armor class. You gain no benefit from wearing armor, but if you are using a shield, you apply its bonus as normal.

To me, this includes any benefit, such as class features or spells that would boost armor and such. (including things such as the Defense Fighting style or the Forge Domain Blessing of the Forge feature. Warfoged armor is extremely potent of it's own, it doesn't need any boosts. Remember that a warforged with a shield has a base AC of 24 (!!!) at level 17+ which is insane. For reference; the Tarrasque has an AC of 25, a Marut has an AC of 22, as do Baphomet and most (if not all) ancient dragons.

Also note that nowhere in the feature it says that you have built-in "armor", except for the part of the table that has the name of the Mode. This is only, however, to indicate that if you have features that require you to be unarmored you'd need to be in the Darkwood Core mode and the other modes count as "armored" (perhaps it's an idea to name it "armored" in stead of "armor" to make this clearer if that is the intent)

Quote from RAJdeBoer >>

Personally I'd say it's not possible. The integrated armor feature specifically states:

Integrated Protection

Your body has built-in defensive layers, which determine your armor class. You gain no benefit from wearing armor, but if you are using a shield, you apply its bonus as normal.

 

To me, this includes any benefit, such as class features or spells that would boost armor and such. (including things such as the Defense Fighting style or the Forge Domain Blessing of the Forge feature. Warfoged armor is extremely potent of it's own, it doesn't need any boosts. Remember that a warforged with a shield has a base AC of 24 (!!!) at level 17+ which is insane. For reference; the Tarrasque has an AC of 25, a Marut has an AC of 22, as do Baphomet and most (if not all) ancient dragons.

Also note that nowhere in the feature it says that you have built-in "armor", except for the part of the table that has the name of the Mode. This is only, however, to indicate that if you have features that require you to be unarmored you'd need to be in the Darkwood Core mode and the other modes count as "armored" (perhaps it's an idea to name it "armored" in stead of "armor" to make this clearer if that is the intent)

Fair points. I may try to get something official later on.

Btw, I read your Homebrew Subclass as 'Darwin Defender' and pictured a scientist with armor, sword and shield lol

Quote from RAJdeBoer >>

Personally I'd say it's not possible. The integrated armor feature specifically states:

Integrated Protection

Your body has built-in defensive layers, which determine your armor class. You gain no benefit from wearing armor, but if you are using a shield, you apply its bonus as normal.

 

To me, this includes any benefit, such as class features or spells that would boost armor and such. (including things such as the Defense Fighting style or the Forge Domain Blessing of the Forge feature. Warfoged armor is extremely potent of it's own, it doesn't need any boosts. Remember that a warforged with a shield has a base AC of 24 (!!!) at level 17+ which is insane. For reference; the Tarrasque has an AC of 25, a Marut has an AC of 22, as do Baphomet and most (if not all) ancient dragons.

Also note that nowhere in the feature it says that you have built-in "armor", except for the part of the table that has the name of the Mode. This is only, however, to indicate that if you have features that require you to be unarmored you'd need to be in the Darkwood Core mode and the other modes count as "armored" (perhaps it's an idea to name it "armored" in stead of "armor" to make this clearer if that is the intent)

 I read the sentence "You gain no benefit from wearing armor, but if you are using a shield, you apply its bonus as normal." differently than you did. 

I think all that sentence means is that putting on any traditional armor gives you no benefit. It's not saying that your built-in defensive layers don't count as wearing armor mechanically. In general, characters are always in a state of wearing armor (armored) or not wearing armor (unarmored). That's why the table of Warforged armor specifies that. That means that features such as the Defense Fighting Style can absolutely apply if you're in either Composite Plating or Heavy Plating mode. 

For the topic at hand, Medium Armor Master specifies that you must specifically be wearing "medium armor," and this table does not explicitly state that Composite Plating counts as "medium armor," just that it counts as "armor." A stickler of a DM could rule that Composite Plating doesn't count as medium armor, but it seems very clear from the fact that it's armor which requires proficiency in medium armor; the intention is for it to count as medium armor. So I'd say yes, Medium Armor Master works with Warforged. 

The question of whether or not the Warforged Integrated Protection feature is absolutely bonkers is a separate issue. It's insane! As a level 1 fighter with a shield and the Defense fighting style, I could have an AC of 21, and without any magic items, that AC becomes 25 by level 17. I think that's insane. I actually made a separate thread discussing how to make it less crazy overpowered. My opinion is that it ends up being okay if you just use half your proficiency (rounded down) instead of the whole proficiency bonus. Those numbers I brought up earlier (AC 21 and 25) become AC 20 and 22, which is still high, but that's with a character that's clearly optimized for having a high AC, and it's well within the domain of what's reasonable given 5e's bounded accuracy design principle. 

Thanks everyone for replying to this thread I did later on try to see if the feat does work with the medium armor that the warforged gets, and it seems like at least in the character sheet on beyond they do get that benefit of having the +3 modifier in dex. I hope they clarify this soon.

Also I found out with the integrated protection the defense fighting style doesn't increase your ac, but for some reasons the medium armor master works. I really hope they set somethings strait and do an update for the warforged.

Nowhere in integrated protection does it suggest that you're considered to be wearing armor in any way. There's benfits of this (you can use heavy plating as a multiclassed low-wisdom monk for a better AC, without losing your martial arts benefits) but also drawbacks (can't benefit from the "x armor master" feats). 

I just found out that Keith Baker actually released an FAQ on the Wayfinder's Guide to Eberron. Seems like I was wrong. Here's the relevant answers:

Does the Warforged Heavy Plating Integrated Protection work with the Fighter’s Defense Fighting Style? Unclear on if (armor) means you’re “wearing armor” or not.
The intent is while you are using darkwood core you are not considered to be wearing armor for purposes of game effects such as Unarmored Defense, while you are considered to be wearing armor when you’re using one of the plating modes. However, as written Integrated Protection doesn’t allow you to benefit from the Defense Fighting Style. This won’t be changed until people have a chance to provide feedback on the race mechanics as they stand.

Composite Plating and Heavy Plating both say “Armored” but do they count as medium and heavy armor respectively? Specifically does a warforged Barbarian in Heavy Plating mode lack access to the benefits of rage?
As written, the current version simply specifies that plating counts as armor, not that it counts specifically as heavy or medium armor. So in this version, a warforged barbarian can rage while in the heavy plating mode… though they will have to acquire the heavy armor proficiency before they can use heavy plating.

So the Defense fighting style and Medium Armor Master should not work with Warforged. Obviously your DM can rule how they want, but it's interesting to read Keith's ruling on it. 

Thank you for telling me about the FAQ Keith did, I hope they are planning on posting the FAQ to dndbeyond a little more since I would have no idea that it was there unless you pointed it out to me. Also it seems like dndbeyond is still letting me get the extra 1 ac with the medium armor setting with the feat.

Does this mean that the Mariner fighting style works with all 3 plating modes?

This thread is moot and shouldn’t have been necro’ed. Warforged no longer have this attribute