Inside Constraint Manager select Physical, Physical Constraint Setup and click the via cell for the Default PCS. All nets pointing to this constraint set will then inherit the new via settings.

In the Nets, All Layers you'll be able to change what constraint set is being used.


In the Physical Constraint Set section you setup constraints sets.

    A Constraint set is a placeholder for a specific set of constraints (widths, via types etc.).
    You can create as many constraints sets as you want.

In the Nets section you specify what nets should refer to what constraint sets

All constraints from the constraint set will be inherited by the nets refering this constraint set.
Changing a constraint value in the constraint set will change it for the nets refering to the constraint set 

Exceptions are overrides which are marked in blue; they will never inherit anything from constraint sets. You can restore the inheritance behaviour by (clear) or deleting the value of the particular field