I think I accidentally changed my Fallout 4 Root Directory's files without realizing it when I used Fallout 4 Tweaker. The files it over-wrote are Ultra.ini, High.ini, Medium.ini, and Low.ini . If you have DEFAULT version of those files, could you please upload them or PM me and I can provide e-mail. They are very small files...

Just delete the files and then verify the game cache. Steam will download the missing files.