This is the proof that Kaido used his Awakened Form against Luffy
First of all let’s take a look at Kaido’s hybrid form, especially the face. His face on hybrid form has the same features as his regular face: sharp nose, “normal” eyebrows, and regular teeth (excep the fangs which grow larger.)
However, in Chapter 1037 it’s possible to see for the first time what I believe are glimpses of his awakened hybrid form. See the following image, notice the increased muscularity and above all, the different facial features: rounder nose, jagged teeth, and “beast-like” eyebrows.
Kaido’s beast form – notice the similar eyebrows to the “awakened” hybrid form
In Chapter 1042 the same form is also shown in certain panels, after Kaido launches a powerful attack.
It has also been stated, in the Kid & Law fight vs Big Mom, that using an awakened devil fruit consumes an important amount of stamina so I state that Kaido uses his awakening only for certain attacks, to make them stronger and more destructive, as awakened Zoans have enhanced physical stats.