From what I've read you can surely get higher than 70fps and about 70-100-ish
A few redditers posted their fps and I quote averages
"about 85fps on pretty much ultra settings at 3440x1440"
"70-100 FPS on BF1 Ultra is normal for a GTX 1080."
"about 75 in Witcher 3 with hair works off, 110 in Overwatch with AA on medium, 75 in GTA V with AA off and everything else maxed, 90 no problem on Fallout 4 maxed."
"I play BF1 at 3440x1440 at ultra with about an average of 80fps, maybe drops to 70 or 60 if alot is going on. On FH3 I get about 60-80"
Hope I helped you hit the best answer if I did
And Hope you enjoy your future build