Namely, I'd like to know if the +20 to your next attack roll with True Strike is applicable to either of the Perfect Strike rolls, at your discretion, or if you are forced into it applying on the first roll of Perfect Strike?
You add it to both
Perfect Strike allows you to roll "your attack roll", the thing True Strike modifies, twice; It does not cause you to make two separate attack rolls. Since it is a single roll rolled twice you get the +20 to both rolls. In the odd event you roll a critical threat with one of the rolls you still add the +20 to the other roll that is now your critical confirmation roll because it starts off as 'your attack roll' then gets used for something else.
Perfect strike states:
You can roll your attack roll twice and take the higher result.
As such it is still one attack roll that is rolled twice. By that you can roll twice, choose the higher and then add the +20 to the result.
Would it say that you make two attack rolls only the first could gain the bonus but as both die rolls are the same attack roll you can choose.