Can someone help me get the best optomisation settings for Fallout 4?

I bought the game a few days ago it automatically put it on ultra. I got in game played the start then a few hours later it started dropping frames. So I put it on high with god rays off shadow distance on medium and it was fine... for a bit. Now I have it on medium and it's starting to run shit again.

Does anyone else have these issues? what could cause it?

I use a nvidea gtx 960 2gb

i5 quad core 4460 3.2ghz

and 8 gigs of ram

forgot to add i did the nvidea geforce experience optimise thing and it still ran like crap