Easy are very tight on One Bag Only (and a bag of airport shopping in some airports).
(I know that's changing soon for Speedy Boarders, but I expect them to remain very tight on non-speedy-boarders).
They are less tight on size, I've definitely seen some pretty oversize bags, especially backpacks that don't look like "large suitcase". As noted above your mileage may vary, but they're not very rigorous on size.
But really, if your bag is bigger than the IATA carry on size, just check it in and get over it. Easy have never failed to give me my bag back on arrival (except the one time the Schiphol luggage handling had a fire and no bags could be handled) so they can be relied on.