Actually every where the term 'ben Elohyim' is used is a reference to angelic beings regardless of the location.
Yes it was angels that had sex with human women that created the giants and mighty men both pre-flood and post flood. Those events post-flood is where the pagan gods came from. That is my area of specialization, the ancient paganism that battled against Israel and was opposed by the prophets all over the OT.
There are many references in scripture that support that. Many of those references get missed by most readers. It takes serious study to understand those references. For example, the pre-flood angels that sinned were called Watchers. Watchers are referenced several places. One that most people miss is in the story of Balaam and the donkey. Balak takes Balaam to 3 different high places dedicated to 3 different members of the Baalim (plural of Baal, the entire pantheon) to try to get him to curse Israel. One of those places was the 'field of Zophim' on Mt Pisgah. Pisgah is a reference to a sex act with the goddess Asherah, ie 'mother earth'. Field is a Hebrew idiom for womb, the place the seed is sown and Zophim is the Hebrew word for Watchers. The location of that sacrifice was at the 'womb of the Watchers' of the goddess Asherah, the mother of Molech and Ashtoreth as well as grandmother of Baal. Molech, Ashtoreth and Baal were post flood nephilim born of Asherah by a post-flood Watcher. My understanding is that Watcher is one of the four angels bound at the Euphrates that gets let out in Revelation and was bound at Babel, the source of post-flood rebellion and source of the ancient paganism.
Another source of great knowledge about the actions of the pagan gods is in name meanings of cities and places in the land of Canaan. Doing a word study of the places mentioned in the book of Joshua is a good place to start. There are many references to the 'gods' having children. One city name references the 'children of lightning(one of the gods)'. Another references the 'god who scatters his seed', a reference to them having children. Even the OT Cockatrice has the 'fiery flying serpent' as his fruit/child/offspring.
All the paganism of the ancient biblical peoples followed the same group of gods but they followed them under different names/titles in different languages that got split at Babel. For example the Canaanite goddess Anath was the Egyptian goddess Neith was the Greek goddess Athena. Asthoreth of scripture was Astarte, Aphrodite of the Greeks, Diana Luciferah of the Romans... Nebo of the Babylonians was Thoth of the Egyptians was Hermes of the Greeks...
Lucifer is just a latin epithet of an ancient pagan sun god meaning 'shining one' basically equivalent to Pheobus in the Greek, an epithet of Apollo, ie Apollyon of Revelation, king of the pit. Even Baalzebub, 'lord of the flies', is a reference to the plague bringer by insect plague while Apollo means 'destroyer' and he was a destroyer by insect/rodent plague and even Molech is a reference to the same deity in the Canaanite pantheon. Lucifer isn't 'ben Elohyim' but 'ben Shachar' and Shachar was a Canaanite deity called 'Morning' who was Hadad, 'the thunderer' to the Syrians and Zeus to the Greeks.
The ancient cuneiform is full of references to the angels that lived with man pre-flood and reference the four Apkallus that lived among men post flood, the four divine rivers that watered Eden. The same sources also call Hadad (the thunderer) and Shemesh (sun god) the ajudicators, ie Satans while we have one Satan cast down 'as lightning', ie Hadad the god of lightning and thunder replaced by his son, the sun god.
Lucifer himself, the current Satan is just a half-breed Nephilim ghost not some mighty angel that rebelled. He thinks he is a god but he is in actuality only a man and a dead one at that.