In the light of the Angmar Faction being released, I have started wondering if its style is or not in coherence with the general Lord of the Rings style. There are many elements who seem borrowed by other fantasy titles such as Warcraft, for example.
Angmar is one the faction with the fewest information (Lorewise speaking). We know of it but not it exactly. Part of it was inhabited by Men, according to the Tolkien Gateway they were thought to be somehow related to the Easterlings (but even that is not sure). Others assume that they were Black Numenoreans. Still, nothing is clear. However, gathering and organising certain points, we might actually come to imagine a much more lore-friendly Angmar.
The first, greatest mistake that the Angmar faction has inherited from its vanilla concept is the usage of Sorcerers. Curious about the role of magic in the Lord of the Rings, I opened Tolkien Gateway which is pretty much the wikipedia of the book and authentic Tolkien sources. I found this rather interesting except from one of Tolkien's Letters(Letter 155):
"a difference between the use of 'magic' in this story [The Lord of the Rings] is that it is not to be come by by 'lore' or spells; but it is an inherent power not possessed or attainable by Men as such."
So you do understand why I find Magic as used by Sorcerers quite disturbing, lorewise. The only known magic used by Angmar is the Witch-King's ability to raise the Barrow-Wights (and that is, luckily, quite achieved by your Barrow).
Furthermore, I oppose to the exaggerated use of Snow & Ice. It quite looks as if it were Warcraft. I would imagine Angmar as a faction in a semi-unnaturally dark and gloomy winter - a Mordor of Cold, cold and snowy aswell but more dead rather than truly white covered in snow. Maybe a little like Dunharrow. Something creepy, not Northrendish. Furthermore, Angmar means Home of Iron, so the lots of Iron we've seen in the Mordor style(architecture and units) would be fit for Angmar aswell (see below). (The atmosphere is highly related with unit design and architecture, so a more clear picture will be provided below).
Third - Angmar's Armies. Angmar's armies in vanilla RotWK were made of Thrall Masters who summoned either clansmen either orcs and then there were Black Numenoreans, Snow & Hill Trolls. Your system of Settlements covers perfectly the relation that Angmar forces and Rhudahur Hillmen had. To that, no objection. I wonder, however, whether the appearence of the Men of Carn Dum is quite "Correct". I understand that there is no Movie reference of how they would look like, BUT, an illustrator, John Howe, has some independent illustrations of the Mouth of Sauron, the Witch King of Angmar and the Black Numenoreans. These concept arts are not similiar to the movie depiction of the Witch King and Mouth of Sauron, but as you can notice, they are quite similiar to the Mordor Style in general. Thus they would make an excellent basis for the development of Carn Dum soldiers and Heroes.
Lastly, I would like to cover the topic of Architecture. There is absolutely no trace in Tolkien's works about the Architecture of Angmar, but we can build one. Where from? Well, starting first from its name Ang-mar (Home of Iron). That and the Iron element in Mordor's architecture in the film. Just see Morannon, Minas Morgul or Barad Dur to understand what I mean. Now, it has to be different to that of Mordor obviously, but then again, not too much. Also, the Fortress of Mount Gundabad in the Hobbit could be a reference. Mount Gundabad is, after all, part of Angmar. I expect them to be of dark-gray/black color (as Mordoric architecture is) and with of course some elements of Ice/Snow/Frost, but not too much - just enought to make it look creepier - not Northrend-ish. The other part, of course, I let to decide to the artist's freedom.
Here, I close my discourse, hoping I have transmitted my ideas clearly and made a quite convincing argument! Good luck with the mod!