In order to get the effective formatting parameter values including inherited you need to use CreatePortionFormatEffective method which returns a PortionFormatEffectiveData instance.
And about PortionFormatEffectiveData class, Immutable object which contains text portion formatting properties. This class is used together with the Portion class to return effective formatting values with inheritance applied.
I hope this will be helpful. please share if I may help you further in this regard.