Masks: A New Generation is probably one of the ones you're going to hear a lot. Monsterhearts and Monster of the Week are two others that are generally considered well made PbtA hacks. Wanderhome has been getting a lot of attention. I like it personally but with all PbtA Hacks they're all only really good at doing what they're designed to do and not very well designed to do what you might want to do if that isn't what they're made for. PbtA is a universal system, the Hacks are not because so much of the PbtA rules are dependent on the themes you want to explore.
Unlikely. Dungeon World is pretty widely considered one of the least recommended PbtA Hack due to a lot of design problems. It was a solid PbtA game when the system was newer but a lot of time has been spent with the PbtA design philosophy and Dungeon World...doesn't pan out. There is a hack of Dungeon World that fixes a lot of these problems however called World of Dungeon which is far better received in the PbtA community.