would like to now if its possible i have both cards for gaming
SLI requires both the same GPU and same video RAM size ... so no, you can't SLI a GTX 1080 with a GTX 1080Ti (two different GPUs and two different video RAM sizes). Sorry.
what about using it just for a second monitor not for sli just to power a second monitor like 1 gpu use one monitor and the other uses a different one
yes, that should work
No. You could SLI a 1080 founders and gigabyte 1080, but not two completely different cards.
you talking about the first thing i asked or the second thing i asked thunder