I became interested in doing the study from listening to him answering folks on this mater. What I learned from the study is that God is always holy and has no part with sin. But I get ahead of myself, must be old age. Jesus taught us that we would not know our wives in Heaven and the context for that discussion gives us the meaning. We will not now them sexually and the reason is because "we will be as the angels."
This singular point plugs a hole no 20 Gauge at close range could inflict. But. then, as you point out... those two angels that ate, drank and, perhaps, conversed with Abram and did speak with Lot. From this account we learn that these are, indeed, in physical form but worthy of note is the truth that they have no part with sin. These angels are not named again but it is, therefore, also, reasonable to read into the scriptures that their service, in these bodies, was completed and they were ten reverted t their Spiritual or natural form.
And to this you will often hear, WHAT! Hear you go back to the Holiness of our God. And yes there are those Fallen Angels of unknown, to us, number. But there is one very important lesson in the Book of Job to be learned, Satan, oft considered, the most powerful of the Fallen could do nothing to Job without the permission of our Heavenly Father. This, God established, principle is never violated in the scriptures and the Word of God is our final authority, until the return of the Author, Jesus.
So it is that the summary goes somewhat like, God is omnipotent and therefore controls everything! (Requires a study all by itself or you will go nuts trying to understand why!) God controls everything, angels can do nothing without God's permission and foreknowledge. (Omniscience) And God allows some evil with His permissive will as illustrated in the Book of Job to teach us who we are and how strong we are and perhaps many other life lessons to grow strong and faithful followers.
But God, because of His Foreknowledge, will never grant any angel, fallen or not, a body to have sex with a human female. There is a good deal more to this issue than people want to study but intelligent answers are never found by reading into scripture what is not there. That is a short prescription for a ride into Hell.