Report back a few data point about the Vueling Visa Up benefit.
When I book the flight through Vueling site with my membership credential, it will display a complimentary one time same day flight change line item. Somehow my vueling membership account is noted that I am a Visa Up credit card owner. I believe none status member will have the option to purchase it (flexi) during the booking process for a fee. Same day flight change is free after paying the fare difference.
Haven't actually take the flight, so I will report back other benefits.