5783- just reading further your previous post- firstly I’m sure The Rebbe knows Tanya better than anyone else. bring the mimale makom of his predecessors etc. So you can look up the references above to see how it
all goes.
Secondly I’m really not that learned, so I’m sorry I cannot give a complete succinct on one foot answer, but according to what I’ve learned in derech mitzvosecha- shoresh Mitzvas hatefilla- (sorry there’s49 chapters- I’m in the middle so far, but probably around 10) I remember that Hashem is one and there’s no levels, just different expressions of His Oneness- just like I might decide to give (chessed) or not to give (gevura) but ultimately it’s me deciding and doing whatever- so too everything from above Atzilus down through Atzilus etc is Hashem Himself using different forms of revelation/ expression. But it’s all Hashem which is why we say Keil referring to Hashem as He is kind- and not davening to the midda of chessed in Atzilus itself which could be ע״ז ח״ו. ע״ש