Probably not extremely well. Maybe well enough if you don't mind it.
With two 1080p monitors your resolution would be 3840x1080. You could probably see 60fps on medium settings for most AAA titles.
Trying to put this in a perspective. That's 4.14 megapixels. My monitor is 3440x1440 (4.95 megapixels) and requires a 1080 to run most games at 60fps on Ultra. 2560x1440 is 3.9 megapixels and a 1070 will usually run pretty much everything at Ultra 60fps on that. So I would say again, medium for 60fps maybe a little lower.
I think a 1070 might have a little trouble on select games at 3840x1080 on Ultra, but probably few.
I personally think Ultrawide resolutions are the way to go, resolution be damned.