Jesus is God in the flesh, but what was he like physically, if that’s the right word to use, before the incarnation? I ask this also because of the appearances of God in the OT, yet we are also told in John 1:18 and John 6:46 that no one has seen God, so is it safe to say that it was Jesus whom they saw?
That’s correct. Even Moses was not allowed to look upon the face of God but was hidden in the cleft of the Rock while He passed by. (Exodus 33:18-23) Jesus made several Old Testament appearances, usually described as The (not an) Angel of the Lord, but we’re not given a physical description. In John 14:9 Jesus told His disciples that having seen Him, they’d seen the Father.