I like the first wireframe better, even though the other two are probably "cuter". The reason for that is mostly just about UI visibility. In the current wizard-based Field Papers UI, the things that you can modify when creating an atlas are spread across a bunch of pages, so it's hard for a user to get an overview of what factors they can change. The first wireframe you made basically solves that problem at one stroke because everything is right there and visible. The other approaches with buttons and stuff sliding in and out are just as discoverable, of course, but there's little enough "stuff" in the Field Papers UI that I think it makes sense to just present it right there to the user all in one go.