/. . . Continued
Moses 6:
53 And our father Adam spake unto the Lord, and said: Why is it that men must repent and be baptized in water? And the Lord said unto Adam: Behold I have forgiven thee thy transgression in the Garden of Eden.
54 Hence came the saying abroad among the people, that the Son of God hath atoned for original guilt, wherein
the sins of the parents cannot be answered upon the heads of the children, for they are whole from the foundation of the world.
Moroni 8:
4 And now, my son, I speak unto you concerning that which grieveth me exceedingly; for it grieveth me that there should disputations rise among you.
5 For, if I have learned the truth, there have been disputations among you concerning the baptism of your little children.
6 And now, my son, I desire that ye should labor diligently, that this gross error should be removed from among you; for, for this intent I have written this epistle.
7 For immediately after I had learned these things of you I inquired of the Lord concerning the matter. And the word of the Lord came to me by the power of the Holy Ghost, saying:
8 Listen to the words of Christ, your Redeemer, your Lord and your God. Behold, I came into the world not to call the righteous but sinners to repentance; the whole need no physician, but they that are sick; wherefore, little children are whole, for they are not capable of committing sin; wherefore
the curse of Adam is taken from them in me, that it hath no power over them; and the law of circumcision is done away in me.
9 And after this manner did the Holy Ghost manifest the word of God unto me; wherefore, my beloved son, I know that it is solemn mockery before God, that ye should baptize little children.
10 Behold I say unto you that this thing shall ye teach—repentance and baptism unto those who are accountable and capable of committing sin; yea, teach parents that they must repent and be baptized, and humble themselves as their little children, and they shall all be saved with their little children.
11 And their little children need no repentance, neither baptism. Behold,
baptism is unto repentance to the fulfilling the commandments unto the remission of sins.
12 But little children are
alive in Christ, even from the foundation of the world; if not so, God is a partial God, and also a changeable God, and a respecter to persons; for how many little children have died without baptism!
13 Wherefore, if little children could not be saved without baptism, these must have gone to an endless hell.
14 Behold I say unto you, that he that supposeth that little children need baptism is in the gall of bitterness and in the bonds of iniquity; for he hath neither faith, hope, nor charity; wherefore, should he be cut off while in the thought, he must go down to hell.
15 For awful is the wickedness to suppose that God saveth one child because of baptism, and the other must perish because he hath no baptism.
16 Wo be unto them that shall pervert the ways of the Lord after this manner, for they shall perish except they repent.
This mercy is also extended to those who have ignorantly sinned, not knowing the will of God, for they are more or less in the same situation as Children are:
Mosiah 3:
11 For behold, and also his blood atoneth for the sins of those who have fallen by the transgression of Adam, who have
died not knowing the will of God concerning them, or who have ignorantly sinned.
12 But wo, wo unto him who knoweth that he rebelleth against God! For salvation cometh to none such except it be through repentance and faith on the Lord Jesus Christ.
So as you can see, there is no difference or disagreement between the doctrine of the original sin as taught in the Book of Mormon, and in other scriptures and teachings of the church. This idea that LDS doctrine has “changed” between the Book of Mormon and its later history or scripture I am afraid is a bit of a myth invented by apostates and anti-Mormons to lead people like you astray.

If you are seriously interested in learning about Mormonism, I suggest you learn it from Mormons, not from Mormon apostates and anti-Mormons.
That clause in the LDS Articles of Faith:
“We believe that men will be punished for their own sins, and not for Adam’s transgression” which you had mentioned is designed to emphasize this fundamental difference between LDs doctrine and traditional Christianity. So you had judged it correctly; it does repudiate the doctrine of the original sin as taught in Catholicism, but not as taught in the Bible.
zerinus