Bethesda Softworks has confirmed today via Twitter that Fallout 4 is 1080p/30fps on PS4 and Xbox One. The publisher also revealed that PC players won't be limited in any way regarding resolution and fps.
As for mod support on PS4, director Todd Howard states that it's in Sony's hands to decide whether or not the PS4 version will support mods. "We will be. Well, we're going to make every effort to. If Sony says no, we won't, but I don't think they will," said Howard. "But, you know, it will come out on PC first. So early 2016, the creation mod for the PC, and then we're going to make that work on the Xbox One, and then we're going to do the PS4 version."
Fallout 4 releases worldwide on the 10th of November on PS4, Xbox One and PC.