You cant sli two graphic card with different chip but you can sli two same chip graphic card from different manufacturers eg. You cant sli a 980ti with 1080 but you can sli two 980 from different manufacturers
not yet. in the future it will work but right now no. it's something that has to be coded with dx 12 and so far only AoS has worked on it. they got it going but i don't think it made it into the final release, though i may be wrong there as i don't own the game.
in time it may be done more often but right no. the answer is "sorry it no work"
You can't SLI them, but you can Multi-GPU them. Only in Ashes of the singularity would it work though. In the future when more games support Multi-GPU there will be a benefit from having two different cards.
You cant sli two graphic card with different chip but you can sli two same chip graphic card from different manufacturers eg. You cant sli a 980ti with 1080 but you can sli two 980 from different manufacturers