To me, God most high describes the awesomeness of God; His Grace, mercy, love, kindness,goodness etc.
Besides Him there is no other God.
Even much more than our human minds can fanthom and much more than mere words can describe, our God is a great and awesome God.
The Bible says that the heaven is His throne ans the earth is His footstool - Acts 7:49, Isaiah 66:1
He is indeed the MOST HIGH GOD!