1) All caps LORD in the OT is actually the name of God, YHVH …
2) Lord in the NT is Kyrios, It is not the name of God. The Term is used of someone of authority and used also for God depending on the Context.
So yes Paul asked who are you Lord, but not who are you YHVH?
He realized he had encountered someone of great power and authority. He did not believe it was God; considering he thought he was doing God a service and he was sure he knew God.
Rather he was asking who this person of great power was, well Jesus answers
“I am Jesus!” What a turning point for Paul considering he was persecuting all those who would preach or call upon that name.
The Bible tells us that after this glorious and powerful encounter he went about preaching Jesus is the Son of God, not YHVH (Acts 9:20).
The Bible tells us that Jesus is Lord but not that he is LORD meaning YHVH because
Acts 2:36 tells us that God (YHVH) MADE Jesus both Lord and Christ.
No one makes GOD ‘LORD’; nor does YHVH make another YHVH. For YHVH is One!
The clearest passages that show Jesus being called Lord does not mean he is
YHVH the Almighty are the greetings of the Apostles. They say
Blessed be the God and Father of our “Lord” Jesus the Anointed.
We can understand that Jesus although he is Lord he has a God over him. The theme of the New Testament comes from its most quoted Hebrew text…
Psalms 110:1 A Psalm of David. The LORD (YHWH) says to my lord (adoni, human Lord): “Sit at My right hand Until I make Your enemies a footstool for Your feet.”
This same Jesus has God raised from the dead and made him both Lord and Christ!