I haven't had too much time to play the mod yet, so before I give my feedback on what I've seen so far I'll first jump in the discussion about the Swan Knights, Gondor armour and so on.
Firstly, I am pretty sure (but Tolkien lore gurus can correct me if wrong) that the armour of the Gondor soldiers (& others) in the LOTR in the books alone was meant to be on the tech level of 11-12 centuries. So the last two images above (the man-at-arms on foot and the mounted croissant
knight) are not representative of Tolkien's vision.
On the other hand, the Gondor armour represented in the movies is of a later tech level with all the plate.
The modders clearly took directly or were inspired from the 6 movies where they could, but obvously had freedom where units were not shown on screen. The Swan Knights were not shown. So there was freedom in how they were represented.
Whilst it is very important, I believe, that units in the mod which weren't shown on screen appear like they have some relationship with ones that were shown (e.g. heraldry, bits and pieces of equipment, etc) this relationship isn't necessarily simple or linear. E.g. the fact that Swan Knights are considered elite doesn't directly mean that they wear heavier armour than the troops from Minas Tirith. Remember that the Gondor soldiers from the movies are ones that are only based in Minas Tirith. The rest probably would be more like the militia (with a bit more chainmail) and the regional troops from the mod.
To sum up, the modders could take two different paths, each choice being fine. One, match the unit (Swan Knights in this case) directly to the movie soldiers with heavy armour and closer look to the regular Gondor troops and look less at the books. Or look more for inspiration to the books and less at the movies and choose more creative freedom.
It's not strange that the Swan Knights are less armoured than troops from Minas Tirith, far away to the north east. They could be more skilled in both riding and fighting and value mobiliy because they have to respond quickly to coastal raids by Umbar pirates along the coast.