Since LFP traction bars keep the pinion angle from changing, is it imperitive to still have the proper pinion angle. Assuming the pinion is "close" to what it should be, within a degree or two is that still ok?

The proper angle should be -2, is that correct?

 

it will still change but not nearly as much as a truck without bars. but it is best to get it dead nuts in a static state so you know everything will be fine

 

Correct, -2 to -4 will be very good. It will not change nearly as much. You do want some slight negative angle. Less than 1 degree can cause wear issues since the needle bearing would move little and thus not spread the wear evenly.