How would Mormon christology be classified? Is Mormon christology Trinitarian in the sense of seeing Jesus as having always existed? Or is it Arian as seeing him as the first being created by God and used as the agent in creation of everything else? Is it adoptionist in viewing Jesus as being born a mere man and exalted or "deified" at some later point?  Or is it a type of Sabelianism (i.e. Jesus being a man but with the Father dwelling in him)?  Does it accept him as the Platonic logos?
None of the above, Mormon christology is Mormonism.

Although this wikipedia article names The Church of Jesus Christ of Latter-Day Saints as a modern Christian group which may be seen as espousing some of the principles of Arianism. 

Latter-day Saints believe God the Eternal Father to be our literal father in Heaven, the father of the spirits of all mankind, just as literally as our fathers on earth are the fathers of our bodies. Jesus Christ is the eldest spirit child of our father in heaven, and only begotten in the flesh, chosen before the creation of the universe to be the saviour and redeemer of all mankind. 

Below is an excerpt from chapter 4 of the LDS Sunday school doctrines of the gospel student manual.


  Jesus Christ, the Son of God
  
  Jesus Christ is literally the son of God the Eternal Father.
  
  
  Jesus Christ is the firstborn spirit son of God (see D&amp;C 93:21; Colossians 1:13–15; Hebrews 1:5–6).
  Jesus Christ is the only begotten son of God in the flesh (see JST, John 1:1, 13–14; 1 Nephi 11:14–22; Jacob 4:5, 11;
  Alma 5:48; D&amp;C 20:21; 76:22–24).
  
  
  Jesus Christ is a being of glory, might, and majesty.
  
  
  Jesus Christ has a resurrected body of flesh and bones (see D&amp;C 130:22; Luke 24:36–39; 3 Nephi 11:12–15).
  Jesus Christ possesses all power in heaven and on earth (see D&amp;C 93:17; 100:1; Matthew 28:18; 1 Peter 3:21–22).
  Jesus Christ possesses a fulness of the perfection, attributes, and glory of the Father (see 3 Nephi 12:48; D&amp;C 38:1–3;
  Colossians 1:19; 2:9–10; D&amp;C 93:4, 12–17).
  Jesus Christ is the light and the life of the world (see D&amp;C 88:5–13; 93:2, 9; John 1:4; 8:12; 3
  Nephi 9:18).