Jesus was a man and yet a son of God. So biblical evidence would suggest yes angels can appear as men.<quoted text>
I don't see that in the KJV. Sons of God are just men.
We are all sons and daughters of God. I don't even see the word Nephilim in the KJV.
Note: this verse
Be not forgetful to entertain strangers: for thereby some have entertained angels unawares.
And he lifted up his eyes and looked, and, lo, three men stood by him: and when he saw them, he ran to meet them from the tent door, and bowed himself toward the ground.
5 As they entered the tomb, they saw a young man dressed in a white robe sitting on the right side, and they were alarmed.
2 There was a violent earthquake, for an angel of the Lord came down from heaven and, going to the tomb, rolled back the stone and sat on it.
3 His appearance was like lightning, and his clothes were white as snow.
4 The guards were so afraid of him that they shook and became like dead men.
5 The angel said to the women, "Do not be afraid, for I know that you are looking for Jesus, who was crucified.
6 He is not here; he has risen, just as he said. Come and see the place where he lay.
Sons of God could mean angels or men it seems depending on the context.
So it could be said that some of the fallen angels also could have been men also from my reading.