While both collars/spacers are essential for operation, the right collar/spacer (left if looking at the front of the bike) is the one that properly positions the wheel centrally.
The other collar/spacer provides proper positioning of the other fork leg.
So don't accidentally swap the collars/spacers during reinstall.
If the axle mark doesn't properly align with the left fork leg (right if looking at the front), the stop immediately and determine why.
If properly installed, the fork legs should never be pulled inwards when tightening.
This will put them in a bind and will never work properly (actually, quite the opposite).
Also, while you have the wheel off, use a clean shop towel to clean any road grime from around the seal areas and apply some fresh grease to the seal lips, plus clean the collars/spacers as well.
With the wheel off, this can provide an opportunity to allow grit into the seal area.
So make sure the seals and collars/spacers are nice and clean during assembly.