I haven't flown Vueling, so I can't say anything about them. I'm providing the following information in case Vueling isn't your only option.
In the summer of 2019, I chose to fly from Porto to Barcelona on Ryanair and from Seville to Amsterdam on Transavia. In both cases I checked my Eagle Creek 2-wheeled 53x35x20 cm International bag when I made the reservations online from the US. It costs much less doing that than doing it at the airport. I typically carry-on only, so checking a bag is somewhat scary for me, but each flight was nonstop, so I wasn't too concerned.
Note that you really pay a big price if you try to take something on board that is too big or too heavy. I was amazed at how long the lines were for the people with enormous suitcases. What were they thinking? Those of us who just had our personal items were put in a separate line and zoomed through.
Both flights were cheap even with the cost of checking the bag. Doing everything online and printing my tickets at home worked well as did everthing else involving the flights. As for comfort, Transavia had much better seats than Ryanair. I was 73 at the time and better "padded" than I am now at 78. The flights were relatively short, but I won't fly Ryanair again if I can avoid it.