If you have not tried it, have you set the launcher exe in NVidia Control Panel to use the High Performance GPU ?
If no, then that will probably sort you out.
If yes, and you still have the problem ...
Join the club http://www.gamesas.com/topic/1544248-bug-report-index-pc/page-12#entry24525362
I have sent detailled reports to Bethesda ( via the contact form aswell as the bug report index linked )
Also to NVidia
And to MSI
One of them should be able to help, unless they all just sit back and blame each other, hopefully one day we will get to the bottom of it. Optimus machines are a PITA, but I seem to recall the situation was the same for Skyrim users on similar machines when that game was first launched, so I think either NVidia or Bethesda need to update something to resolve the issues
One thing you can do in the mean time - Let the NVidia installer install Geforce Experience ( I know I dont like having another background systray tool running either ), get it to recognise you have Fallout installed, and use its Fallout 4 profile for your machine
It will not be perfect, but at least you will get a ball park setup, and can tweak it a bit afterwards until someone fesses up and solves the launcher using the NVidia GPU so it gets the settings correct