If you're expecting more info on how mods will work in Fallout 4, you're going to have to wait.
Fallout 4 will supports mods on PC, with those mods being available on the Xbox One and PS4 eventually.
This we know. And we're going to have to remain patient for more news on mods until after the game has been released, according to Bethesda's Pete Hines.
@Sepherchorde If it's ok with you, we're gonna focus on the game release first and talk about mods when we've figured some stuff out.
— Pete Hines (@DCDeacon) October 26, 2015
Fallout 4 is out for PS4, Xbox One and PC November 10. If you're looking around for a demo, it's not going to happen. It's just "not possible" according to Bethesda.