There are significant differences between different eras of Greek language. Classical Greek especially can occasionally lead the student of biblical (koine) Greek down the garden path and into a cul-de-sac. Lots of questions about examples of that have already been answered on this site, so I will not go into that. Sticking just to the Greek used in the last book of the Bible, Revelation, it will be seen that there are nuances of meanings for every description of the dragon in that book. Yet given that the great adversary of God in the book of Revelation is the one, same entity working unseen in and through agencies he has raised up to wrest control of God's creation from him, there is enough detail in the book of Revelation to answer this question from the three texts you cite, especially as you ask what the apostle John and first century Christians would understand.
You ask if the Apostle John's use of the term δράκων [implied] anything supernatural and the answer to that is a straight 'yes' because the whole of Revelation was about supernatural, invisible entities, powers and battles going on in the unseen realms. But 'magic' has nothing to do with that last book of the Bible, neither has pagan superstitions.
Consider the significance of δράκων (drakon) appearing 13 times in the New Testament, but never outside of the book of Revelation. It is written eight times by John in Revelation chapter 12 alone. He is spoken of as 'great red dragon' once, 'great dragon' once, and 'dragon' six times - all within chapter 12 alone. This is where the arch-enemy of God appears, for the first time. Seven more times in that one chapter he further appears: as 'serpent' twice, as 'old serpent' once, as 'accuser' once, as 'devil' twice, and as 'satan' once.
Chapter 12 directed John, the Christians alive at the end of the first century who read this, and all Christians thereafter till this very day, as to how this invisible spirit is to be identified and viewed. He remains hidden in John's writing until the vision of the heavenly woman about to give birth in the mid-heavens to a male child causes his appearance as a symbolic great, red dragon, wanting to destroy the male child at the moment of birth. John and Christians then would have not had a shadow of doubt but that this indicated what had happened invisibly in the spiritual realms when the one appointed to rule the nations with an iron rod appeared as per Psalm 2 - "the seed of the woman" as per Genesis 3:15. Here is commentary on this dragon as detailed in chapter 12:
"That this monstrous dragon cannot be seen, takes nothing from the
symbolism. This is what comes to light at the birth of the one
appointed of God to rule the nations with a rod of iron. At the
nativity of the King of kings to whom the crown rights of all the
nations pertain, the heir who is to rule the world, the adversary is
galvanized into such rapacity that no figure could be more suited to
portray him than a 'great red dragon'.
Never before. But at last, with the birth of the chosen and elect
heir, the hitherto unbroken sway of the adversary, in contention for
world dominion, not only is contested, it is downright denied and
challenged root and branch. This brings out the dragon...
Christ is come to take it from him, for the adversary obtained it by
subtlety, rebellion, and wickedness, but God had chosen his Anointed,
appointing to him the crown rights of world dominion. I say, this
brings out the dragon." The Revelation of Jesus Christ, pp 292-3,
All Christians should be so familiar with all the prophecies in the Bible about the battle between God as his invisible arch-enemy, that when the final, epic prophecies John wrote down are given, all the pieces should fall into place. It should all make sense, especially with other descriptions, like 'serpent' 'accuser' 'devil' and 'satan' applying equally to this symbolic dragon.
All of those first century Christians would know enough of pagan ideas about Bel, and Dagon etc (gods of Old Testament times) so as to shun everything those polytheistic pagans taught about dragons and serpents. Why would Christians of today seek to do the exact opposite and delve into pagan literature about this?
In the New Testament the Greek ὄφις (ophis) means a snake/serpent. In 2 Corinthians 11:3, Christians knew that it was the serpent that beguiled Eve through its cunning, but they also knew that the spiritual seed of the woman would crush that spiritual serpent in its head - destroying it. That was what guided their beliefs about the serpent. They would not be beguiled by pagan legends or beliefs. The five times ὄφις (ophis) occurred in Revelation, would confirm all of that to them.
The Revelation would build up their faith that satan's wrath against them would only be permitted by God for so long, then God would cast him and his legions into eternal judgment, but for their eternal deliverance. That would be the 'image' that the book of Revelation would give them as to the unseen adversary, out to destroy the people of God, and to usurp the Kingdom of God. Chapter 12 of Revelation would give them a 'picture' of that triumph secured with God snatching the male child up to his throne, so that the dragon was defeated at that instant. Then he was cast down, confined to the Earth, with the next steps detailed, leading to final judgment for all rebels against God. The comfort that would give John and all other Christians would be immense, as it should equally comfort Christians today.