His thoughts on God, what the Godhead was, were static and not set in stone at age 14?
1832 Joseph made his first real attempt to pen down his christian experience. It's an interesting read to see the anguish he stated he went through between the ages of 12 to 15. To me, he intimates he came to the knowledge of apostasy between this age before his vision. Others might read it differently. Here is the account:
http://deseretbook.com/personalwritings/4
In 1835 he said he was visited by a personage who declared Jesus was the Christ and was accompanied by a large volume of angels. Makes no distinction who this personage was, but that it occurred to him when he was 14. This account is found in his personal diary.
In 1838 we get the version we are all familiar with found in the D&C.