SNOMED allows the membership of a set to be made inactive (the concept is considered to be no longer part of the set at this point), independently of the active state of the concept itself. In FHIR elements are deleted entirely when they are no longer part of the ValueSet - a previous version would need to be consulted.
Filtering a ValueSet with ECL during Expansion
No, you can't mix ECL and named ValueSets at expansion time.
But if a ValueSet was based on a ReferenceSet then an implicit ValueSet could be constructed which was the intersection between the members of the reference set and some other ECL.