The question is large in scope. Maybe the moderators will allow some length for this reply.
It is the context of the scriptures which determines whether "sons of God" are heavenly messengers, or earth born men and women. The question includes Rom. 8:16, but we should look two verses up.
"For as many as are led by the Spirit of God, they are the sons of God." (Rom. 8:14, KJV)
Strong's Gr. 5207, hyos - sons, properly - related by birth, a descendant of the father; figuratively - one who is of the same nature or belief of the Father who follows after the commandments of YHWH; likeness of the believer to the heavenly Father; one who is legally an inheritor of the Father. (1)
It is the same meaning which is defined in Luke 20:34-38,
"34 And Jesus answering said to them, `The sons of this age do marry and are given in marriage,
35 but those accounted worthy to obtain that age, and the rising again that is out of the dead, neither marry, nor are they given in marriage;
36 for neither are they able to die any more -- for they are like messengers -- and they are sons of God, being sons of the rising again.
37 `And that the dead are raised, even Moses shewed at the Bush, since he doth call the Lord, the God of Abraham, and the God of Isaac, and the God of Jacob;
38 and He is not a God of dead men, but of living, for all live to Him.'" (YLT)
where those "sons of the rising again", those that are resurrected to eternal life in heaven are those who live to Him, the God of Abraham, Isaac, and Jacob who die no more.
As many people want to ignore the very clear statement of our Messiah that the messengers (angels) in heaven do not marry, nor are given in marriage means they do not have carnal knowledge of each other which rules out the very science fiction fantasy belief that God allowed spiritual / physical hybridization of heavenly messengers with human, earth born women which they mistakenly attribute to "sons of God" in Gen. 6:2.
They fail to consider the listing of all of the righteous MEN in the previous chapter - Gen. 5. They also fail to catch the context of the beginning of Gen. 6:1.
"And it cometh to pass that mankind have begun to multiply on the face of the ground, and daughters have been born to them," (YLT)
The context is MANKIND, and daughters being born to earthly men. The sons of God listed in Gen. 5 began to marry women "of all whom they have chosen" (Gen. 6:2). The continuation in Gen. 6:3 stresses the context again, that God's Spirit would not strive with man's fleshly spirit - "in their erring they are flesh" (YLT).
The context of Gen. 6:1ff is of earth born fleshly men and women, which makes the "fallen ones" of Gen. 6:4 those men and women who walked away from, fell away from God's commandments. Their offspring became the "men of name." They were not led by the Spirit of God (Rom. 8:14).
We must stay within the context. God made it very clear in Gen chap. 1 that all living creatures which He created propagated and multiplied "after its kind". (Gen. 1:11, 12, 21, 22, 24, 25) This is the basis of our scientific system of taxonomic classification of species, genus, family, order, class, phylum, kingdom, domain, etc.
Everything God created multiplies after its own kind, and that includes men and women.
Therefore, which sons of God must be determined by the context of the scriptures, and that includes those "sons of God" of Job 38:7.
Most translations have "sons of God" but some such as the CEV, the ERV, and NIV interpret the words and translate them as "angels." Other translations choose to translate them as "divine beings" (ISV), or "heavenly beings" (NRSV). These other translations are leading a direction of thought toward their beliefs instead of just translating the actual words. The Hebrew word for "sons" in Job 38:7 is Strong's 1121, "ben". It has many uses throughout the OT scriptures depending upon the context. (2)
Job chap. 38 uses a lot of poetry, and poetry has a style in scripture where the first stanza (part a) is repeated in a similar or comparable form in the second half of the stanza (part b) making objects equal to each other.
The context is set in vs. 4, and the time God was speaking of was the time of creation of the earth.
"Where wast thou when I founded earth? Declare, if thou hast known understanding." (YLT)
And the poetry begins in vs. 5..(from the YLT)
"Who placed its measures -- if thou knowest? Or who hath stretched out upon it a line?
From the 1st half - "placed its measures" is equal to "stretched...a line" in the 2nd half.
"On what have its sockets been sunk? Or who hath cast its corner-stone?;" (vs. 6)
From the 1st half - "sockets been sunk" equals "cast its corner-stone" in the 2nd half.
"In the singing together of stars of morning, And all sons of God shout for joy," (vs. 7)
From the 1st half - "stars of morning" equals "sons of God" in the 2nd half.
We could go on in this manner with many more of the verses in Job 38 to see the similes and metaphors of God's poetry. But the point is the context of Job 38 which is still within the time frame of the creation of the earth, before God created man.
So, the "sons of God" of Job 38:7 predate the creation of the earth born, righteous "sons of God," followers of God used in Gen. 6 and Rom. 8. Is the use of the simile for "stars of morning" and "sons of God" just a figure of speech? It is the poetical style of God's scripture which uses much figurative language. Are these heavenly messengers (angels)? Are they the heavenly host which were in existence before God created man? That is one view. But, this one topic may be in the realm of things God has not yet revealed to man.
The scriptures we have been given are centered around the Lamb slain from the foundation of the earth (Rev. 13:8), Jesus Christ / Yeshua, our Savior, Priest, and King. That is the core subject from Genesis through to Revelation, the Aleph and the Tav ("et" Gen. 1:1), the Alpha and the Omega (Rev. 1:8; 22:13). He is the beginning and the end, the first and the last; and the only one who can reconcile us to the Father.
So, the scriptures are concerned with Jesus and the plan of salvation through His sacrifice for all mankind. That does not mean that we have been given all of history, and all of the events that ever happened to every man or creature on earth. There is a great deal we are not told. We only have two verses about Melchizedek in the OT (Gen. 14:18; Psa. 110:4) before we understand more about his priesthood in Heb. chap. 5, 6, & 7 foreshadowing Christ's.
I am hoping that there is a great library God has maintained which we can view when we are gathered home. It may be that we have a freshmen orientation class waiting for us. Gen. 1:1 may very well indicate a previous earth in existence before ours.
"And the earth was without form, and void;..." (KJV)
meaning without shape, and being empty.... God was about to shape it and fill it. So..., what had it been before? And, who were all of the heavenly host? The heavenly host included the Seraphim and Cherubim (Isa. 6:2, 6; Gen. 3:24; Ezek. 10:1,2). The sons of God of Job 38:7 may be much more than just the heavenly messengers.
Concerning the use and translation of the Hebrew "malak" and the Greek "aggelos" as angels - it simply means "messenger," one who is sent. A messenger can be either a heavenly messenger God sent (the Angel of the Lord), or an earthly messenger such as the prophet Malachi (from malak, meaning "my messenger"). It does not always mean a heavenly one. The context rules. For more on this topic see my answer here: hermeneutics
(All bold emphasis is mine.)
- Strong's Gr. 5207, hyos - https://biblehub.com/greek/5207.htm
- Strong's Heb. 1121, ben - https://biblehub.com/hebrew/1121.htm