Fallout 4 won't start (launch) on full screen. Solved !!! 

Full screen solution.
Before
bTopMostWindow=0
bMaximizeWindow=0
bBorderless=0
bFull Screen=0
iSize H=720
iSize W=1280
after
bTopMostWindow=1
bMaximizeWindow=1
bBorderless=1
bFull Screen=1
iSize H=1080
iSize W=1920
Just don't forget change the screen size to yours. If you have any trouble let me know. Thx