PS: The following is not directed at any author. It is merely a unified response to similar questions raised by readers of this book.
Everything below is based on official canon.
1. There is no such thing as "awakening Warp essence."
For the specifics, you can read the debunking posts by the expert Tian Suo. His two articles explain it very clearly, so I will not elaborate further.
His view has also been endorsed by experts such as "nod1."
Here is my own understanding: according to current official canon, the primarchs do contain Warp components, but the official material has never made this explicit.
In the campaign book Eye of Terror: Steel Reign, as shown in the image below, the first sentence refers to the essence of the Warp, not that of the primarchs. This is a matter of grammar.
The relevant content is as follows:
The Warp allows the obsessions of sentient beings to take tangible form.
Daemon primarchs are also Daemons, so they fit the definition of Warp energy gathered around Chaos power as its foundation.
The source of their Daemonic forms is a combination of the Old Man in Yellow's genes, the substance of Chaos power, and their own will.
Since official canon has not clearly defined the composition of primarchs, one may use the term "Warp essence."
But even if "Warp essence" is used to refer to Warp components, that does not mean there is some so-called "awakening" like a Saiyan transformation.
As though there were suddenly a qualitative change and a massive increase in combat power.
There is even less basis for the idea that awakening makes one a minor Chaos god.
In Shadows of Yesterday, it was more like Corax came to recognize and accept the Warp part of himself—something he had resisted because