yeah I'm doing well thanks. Hope things are well with you. Onto your question...
Exodus 33:12-23 is certainly an interesting and intriguing passage. I won't have all the answers here but I'll note a few things and hope it helps in your continual study!
You are right that there are many people in the Old Testament that 'saw' God. For example, Hagar (Gen 16:13); Jacob (Gen 32:30); Moses, Aaron, Nadab, Abihu, and seventy of the elders of Israel (Exo 24:9-11); Gideon (Jdg 6:22-23); Manoah and his wife (Jdg 13:22); Isaiah (Isa 6:1); Ezekiel (Eze 1:26, cf. Eze 10:20); John (Rev 1:17). In connection to this it is interesting that Jesus said:
Joh 1:18 No one has ever seen God, but God the One and Only, who is at the Father's side, has made him known.
Also note concerning God:
1Ti 6:16 (God) alone possesses immortality and dwells in unapproachable light, whom no man has seen or can see. To Him be honor and eternal dominion! Amen.
1Jn 4:12 No one has seen God at any time; if we love one another, God abides in us, and His love is perfected in us.
So I believe that all these experiences and sights of 'God' in the Old Testament were, as you say, experiences of the pre-incarnate Christ Jesus. It is interesting that even a heavenly vision of Yahweh (LORD) that Isaiah had where He saw the heavenly throne and something of the glory of God (Isa 6:1-5) is said in the New Testament to be a vision of Jesus!
Joh 12:41 Isaiah said this because he saw Jesus' glory and spoke about him. (note John 12:40 quoting Isa 6:10)
It seems that the pre-incarnate Jesus would manifest Himself in various ways to these Old Testament saints (sometimes as a man, sometimes as 'the angel of the Lord', and sometimes in some degree of manifest glory). Now Moses had already seen some degree of the shekinah glory of God when he, with the elders of Israel, went up Mount Sinai earlier in Exodus:
Exo 24:9-11 Moses and Aaron, Nadab and Abihu, and the seventy elders of Israel went up (10) and saw the God of Israel. Under his feet was something like a pavement made of sapphire, clear as the sky itself. (11) But God did not raise his hand against these leaders of the Israelites; they saw God, and they ate and drank.
This again was Jesus. So it seems that when Moses asked 'show me your glory' he desired to see, visibly, a greater manifestation of the Lord's splendor and majesty. The Lord responded with:
Exo 33:19-23 And He said, "I Myself will make all My goodness pass before you, and will proclaim the name of the LORD before you; and I will be gracious to whom I will be gracious, and will show compassion on whom I will show compassion." (20) But He said, "You cannot see My face, for no man can see Me and live!" (21) Then the LORD said, "Behold, there is a place by Me, and you shall stand there on the rock; (22) and it will come about, while My glory is passing by, that I will put you in the cleft of the rock and cover you with My hand until I have passed by. (23) "Then I will take My hand away and you shall see My back, but My face shall not be seen."
So the Lord gave Moses a greater revelation of His visible glory (which is an outward manifestation of His character and nature) but Moses couldn't see Him fully for it would be too great for Him and Moses would have died. Thus he was hid in the rock and only got to see the back of God. This alone was enough for the manifest glory of God to be displayed in the face of Moses:
Exo 34:29-30 It came about when Moses was coming down from Mount Sinai (and the two tablets of the testimony were in Moses' hand as he was coming down from the mountain), that Moses did not know that the skin of his face shone because of his speaking with Him. (30) So when Aaron and all the sons of Israel saw Moses, behold, the skin of his face shone, and they were afraid to come near him.
But again, Moses only got to see a fraction of the Lord's manifest glory. We need to remember that when John saw Jesus in the book of Revelation, he said 'and His face was like the sun shining in its strength' and John fell down 'as a dead man'. We can't even look at the natural sun for long without damaging our retinas and having the potential for permanent eye damage. And that is only a small glimpse of the full glory of God! One day of course we will be able to see Him face to face and shall see Him as He is because we will receive a new body and be changed into His likeness!
It is also worth remembering that when the Lord Jesus returns at the end of the tribulation, He shall come in glory:
Mat 24:27 "For just as the lightning comes from the east and flashes even to the west, so will the coming of the Son of Man be.
Mat 24:30 "And then the sign of the Son of Man will appear in the sky, and then all the tribes of the earth will mourn, and they will see the SON OF MAN COMING ON THE CLOUDS OF THE SKY with power and great glory.
If Aaron and the sons of Israel were afraid of Moses when they saw him shine with the glory of God, imagine what it will be like for a God-rejecting world when they see the Lord Jesus come in glory!
Hope this helps. God Bless.