MTG Salvation

If I have a 3/3 golem copy token version of Serah Farron in play from Nexus of Becoming and it transforms, is it then a 3/3 golem copy token of Crystallized Serah?

Yes, sure. The rules now allow tokens created as a copy of a double-face permanent to be double-face with the same two faces and the same face up and switch to the other face when it transforms. But when it transforms, the copy effect does not wear off, so if it had exceptions, those apply to the other face if possible. Here the exception grants artifact and creature types in addition to setting force and endurance, so it is possible to apply. If the copy effect just set force and/or endurance and/or granted creature subtype without granting creature type, like croaking counterpart for example, it would not be possible to apply that to the other face as long as it is non-creature.