[@Blackfridayrule][@The Wyrm]I reread your NS with more attention and it's interesting that both of your ideas can be meshed along with what direction I wanted to go with my elves.
First off, Yelinor are also somewhat a warrior culture albeit nowhere to the extend Azurei are. Their style for skirmishing and infiltration rather than direct combat also reflects how I think about my fighting style. Albeit it's less just due to the numbers and more because I can't see a species with such love for life and longevity to risk it in open combat.

As for Rhaetia given the ancient roots of my nation it's possible that you were once occupied by a Yelinor tribe. Or it could be a tribe of non-Yelinor elves from around the same region. My nation is also supposed to have great skills at shipbuilding. Depending on details the existence of your people might also confirm one of the two competing theories about the origin of Yelinor.
1.) They are the original elves who remained in their magic rich home and gradually changed to what they are now.
2.) They are elves who had wandered North and discovered a magical island which gradually changed them into the Yelinor.
The only conflict plot-wise I can see is the Rhaetians' secret to shipbuilding. Since if it came from Yllend'tollome then most likely that technology is quite frequently seen with Yllendthyr and its subjects.
Although it could be just an ancient technique already forgotten in Yllendthyr or perhaps it was something kept secret and never spread to the other tribes?
We can sure discuss the details. Everything can be worked out.