OWE is worthless on Vueling.
However when you book a codeshare via IB - either miles or a standard paid fare - you will be booked into "Optima" class and get a checked bag and seat selection. However you need to figure out your Vueling PNR - which is different from the Iberia one.
More details here.
https://insideflyer.co.uk/2018/06/ho...eling-flights/