When exploring a bias through Preconception, the conflict is coming from the unwillingness to reevaluate.
When exploring a bias through Attitude, the conflict is coming from how that bias is used to proceed with an approach.
Let's take the example of a woman trying to get ahead in a male-dominated company where everyone (esp. the leadership) has macho / sexist attitudes.
If Preconception was the issue, you could focus on how the woman is actually very qualified but no one is willing to give her a chance because of their prejudice, they see her as incapable and won't re-evaluate even with new evidence.
If Attitude was the issue, you might focus on how some real pig character is able to use his bias against women to get ahead -- making dirty jokes which earn the respect of the boss, etc. Meanwhile the woman takes the attitude that she just needs to ignore the pigs and focus on doing a good job, but it doesn't get her anywhere.
Regarding your first question, you might want to pencil in several choices for Issue (along with Attitude and Preconception it could probably fit Approach, Openness, and several others like Rationalization or Commitment if the focus was on why they compromise). Then use other aspects of your story idea to find the storyform and pinpoint the Issue. (I think this is what Mike and Jim meant by using implied story points.)