From the wikia.
Being born a favored soul has both advantages and disadvantages. Like a cleric, a favored soul has access to her god's divine magic. Unlike a cleric, however, the magic of a favored soul is natural. As such, it is unlikely to be denied by her god. Because favored souls do not need to pray for their spells, deities don't need to approve or disapprove each and every incantation. This and the many divine powers of a favored soul make members of the class quite powerful. Despite these powers, favored souls are often hindered by a sense of inescapable destiny that surrounds their births. They didn't choose their paths and may not want anything to do with their religion. In this way, the powers of a favored soul can be a burden rather than a blessing.
There are cases of FS not even knowing they are a favored soul, people whom grow up in places that may not stimulate a desire to crusade for a specific deity (whom they may not even know exsist). Granted, they may allways feel a pull or such, but they are not -bound- to follow it (unlike clerics who have to actively worship to get anything). Therefore you can be an "un-discovered" favored soul - or something along those lines.
As for the favored weapon... Well, you get a certian profeciency in that weapon, but not mastery or such... A fighter can easily be a favored soul of Torm... but has all his focus on mastering his whipping of people instead, ergo whip > greatsword. (Dont ask me why I chose whip over something more subtle... like a hammer >.>)
The ball is in the favored souls court most of the time, If they actively discover whom they are aligned to, then sure... the god may chose to punish or venerate their deeds based on the FS actions... however... I doubt Torm will start to punish young FS Bob who has 8 int score, grew up in the gutters and is, at present, trying not to starve by feeding on rats from the nearest outlet... Because its simply not Bobs time to shine (Or Torm is ashamed

).