Genesis 22 is a good example of Christ being there in all three senses.
By promise, He is there in the Seed, first promised in 3:15, threatened through sacrificial death but renewed so that in Abraham's Seed all nations will be blessed (22:18).
He is also promised very strikingly in v14. Abraham said the LORD would provide a lamb (v7-8). On this occasion a ram is provided (v13). And "So Abraham caled the name of that place "The LORD will provide." As it is said to this day, "On the mount of the LORD it shall be provided." The Lamb of God who takes away the sin of the world will be provided on that mountain in the region of Moriah (Jerusalem - cf 2 Chron 3:1). And everybody knew about it. They kept saying 'On that mountain the LORD shall provide Himself the lamb.' (It's a reflexive verb, tricky to translate but fascinating all the same!)
By prototype, there is Isaac the very first promised offspring of Abraham. The beloved son. The heir of the promises. He carries the wood on his back up the hill while his father holds the tools of judgement (v6). He is laid on the wood for sacrifice, but through divine intervention Abraham receives him back from death (cf Heb 11:19). And all of this on the third day (v4)
By presence, the Angel of the LORD intervenes. In v12 He sees that Abraham fears God because he didn't withhold his son from Himself (that is, from the Angel). In verses 15-18 the Angel speaks as the LORD, swears by Himself and promises to bless Abraham as above. He both is the LORD but He is also clearly distinct from another Person called LORD. Interesting isn't it - this is the only time the Angel is said to speak from heaven. Christ chose not to come down to this pre-enactment of the cross.
So Christ is present in a mixture of these three ways throughout the OT.
And it's important to highlight all three and to relate them to one another. The Angel is present not as a freaky apparition but as a portent of the gospel work He would do as the promised Seed, the promised Isaac etc. Check out these quotes by John Owen that interweave Christ as actually present and Christ as promised:
"After the promise [of Gen 3:15] was given, he appeared ‘in human form’ to instruct the Church in the mystery of his future incarnation, and under the name of Angel, to shadow out his office as sent unto it and employed in it by the Father; so here, before the promise, he discovered his distinct glorious person, as the eternal Voice of the Father. (John Owen's Works, Volume 18, p220)
[On the LORD's appearance in Genesis 18] Neither is there any ground for the late exposition of this and the like places, namely, that a created angel representing the person of God doth speak and act in his name, and is called Jehovah; an invention to evade the appearances of the Son of God under the old testament, contrary to the sense of all antiquity, nor is any reason or instance produced to make it good. (ibid, p221)
[On Genesis 32:24-30] From what hath been spoken, it is evident that he who appeared unto Jacob, with whom he earnestly wrestled, by tears and supplications was God; and because he was sent as the angel of God, it must be some distinct person in the Deity condescending unto that office; and appearing in the form of a man, he represented his future assumption of our human nature. And by all this did God instruct the church in the mystery of the person of the Messiah, and who it was that they were to look for in the blessing of the promised Seed. (ibid, p225)
[On Exodus 3:1-6] He is expressly called an “Angel” Exod. 3:2 – namely, the Angel of the covenant, the great Angel of the presence of God, in whom was the name and nature of God. And he thus appeared that the Church might know and consider who it was that was to work out their spiritual and eternal salvation, whereof that deliverance which then he would effect was a type and pledge. (ibid, p225)
When we highlight the presence of Christ with the people it is not to minimize the importance of the promise nor the proto-types. Christ is present among them that He Himself might prefigure His promised work. So the OT is not various promises and types moving towards Christ but is Christ Himself striding towards His own incarnation. (Blackham's phrase).
But then why specifically highlight the presence verses?
Well often when I speak about Christ in the OT I mention the promises and people say "Ah yes, but they spoke better than they knew." Sometimes they'll bring up 2 Cor 1:20 and say 'There were lots of promises about all kinds of stuff but, unbeknown to the OT saints, these promises ended up being about Christ.' Of course they never quote v19 which says 'These promises have always been 'Yes' in Christ.' But still the 'promises' route seems to slide off people's backs.
The proto-types route very readily slides off backs too. 'David was David' they say, 'No-one had to know he prefigured the divine Messiah.' Now of course you can quote Gen 49:10, you can point to the immensely exalted ways David is spoken of in the OT, you can do what Jesus did and quote Ps 110 or what Peter did and quote Psalm 16, but still people don't want to admit that the OT saints consciously knew about the typology in which they participated.
And so we turn to the presence verses. And here there is still resistance - "Ok so Jacob knew that the name of the God of Abraham was the Angel (the Sent One) and He was the Source of blessing (Gen 48:15-16). So what?"
But my hope is that banging on this particular point may just soften up an assumption that resists this teaching very strongly. The assumption is that OT saints could not have understood that the divine Visitor who encountered them was Himself LORD and also sent from the LORD. It is assumed that OT saints are effectively unitarian in their understanding. It is assumed that the OT saints had no ability to conceive of 'God from God' the way we do and therefore no conceptual framework for knowing and trusting the distinct Person of the divine Mediator.
My hope is that banging on these verses may just loosen up such a tight set of assumptions, because those assumptions really do straight-jacket these discussions.
It's not by any means the only way by which we should speak of Christ in the OT but it's a significant plank in the argument.