My opponent casts Paradoxical Outcome and targets 2 permanents they control.
I then cast Insidious Will. Now I can just counter Paradoxical Outcome, but instead I want to bounce some of their permanents (for example clearing blockers out of the way). It is clear that I can change the target from 2 permanents to another 2 permanents, but do I need to target the same number of permanents?
In other words can I choose to return none, one or seven permanents?
If I had to redirect the same number would I be able to choose the same target twice and as a result only return one?
Note that this is not a duplicate of "Choosing new targets for a spell with a variable number of targets" as that is specifically for copying spells, not changing the targets of an existing spell.