The angels are beings of the sky. They dont all appear as if humans.
The kruv (cherub) in the context of the Ark of the Covenant appears like an Egyptian sphinx (a specific kind that has wings and the head of a human sovereign). We can see this sphinx in Egyptian iconography, and also in Israel, such as carved into the sides of an Iron Age royal throne, where the sovereign sits between the two kruvim.
However, the kruvim appear in a different form when they relate to Babylon, in the "chariot", a mobile throne that can travel to different locations. There they are blend of four creatures (human, lion, eagle, and bovine), and the head has four faces, one for each animal, facing the four directions of the cosmos. (Possibly, these four cosmic directions relate to the zodiac, such as Leo the lion, Taurus the bovine, Aquarius the human, but then Scorpio is the eagle.)
The Seref (Seraf) literally means "scorching", burning in the sense of searing or incineration, or even in the sense of the venom from a snake or a scorpion, that inflames and causes necrosis. Whether the Srafim are understood as "burning" or "venomous", these are dangerous beings. They ascend higher and higher, suggesting the divine potential is becoming more and more actual within the material world.
In any case, the weird appearances relate to these sky beings being cosmic beings.
