In this Iberia site you can see which extra luggage/free overweight apply based on your Elite status.
https://www.iberia.com/us/luggage/al...aggages-search
Specifically, open the "Iberia Plus customers" tab (below "Exceptional Cases").
As a OWE you do not have free overweight, unless you are IbPlus elite.
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Lounge access for <2 y/o, you are right. Lunge dragon is wrong.
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Fast-track is a messy OW benefit. Technically it's an Emerald benefit. However, some airlines add it to their equivalent OWS tier (like Iberia does to its Oro FF), and some airlines extend that benefit to other OWS flyers.