I think that one is canon. It is just not usually counted as being actively involved in the Blood War.
On a related note, celestial angles totally are a thing. They live in Arcadia and look like this:
Like noob said, it would take much extra work to make the existence of the Wall any palatable.The Wall of the Faithless wasn't created by anyone, it is just the natural endpoint for any souls without divine protection in the Realms. Most gods are extremely frustrated that some souls still end up in it, given that they offer free access to afterlives that are in their opinion obvious paradises.
For a less obvious Borg-like creature, I really love the kaortis. They were originally humanoids, most likely elves or humans, who went to explore the Far Realm in some kind of diving gear. Now they are mostly known for wearing armor assembled from bandages made of a resin-like material they secrete. They also make nests out of the stuff, called kaorti cysts. Their bodies are full of little symbiotes they can inject in other humanoids to transform them into kaortis, and they plan mass assimilation. They are also the creators and masters of various aberrations such as skybleeders, rukanyrs and kaortic hulks.The Oard are totally canon and in their original timeline eventually turn into the Illithid. And I don't care how little sense that makes.
I can imagine them being lead by a female daelkyr who totally looks like the Borg Queen.
Interesting. After seeing the Ood in Doctor Who, who are an obvious plagiary of the illithids, complete with ceremorphosis and elder brain, I am ready to believe this.