>>713144706The Definitive Edition itself doesn't add much, but it has all of the 3DS port's extra content and QoL features. That includes like four new Adventure maps as well as Tetra, King of Red Lions, Medli, Marin, Toon Zelda, Ravio, and Yuga as playable characters. Even with the original Adventure map being rebalanced to be quicker and easier to accommodate a more natural difficulty progression across the maps, it's easily double what was already in the WiiU version even including the DLC.
>>713145110"Padding" where you're unlocking characters, weapons, heart containers, etc. I'm not sure what the difference is.