Simply put no, AMD has some exceptions to the dual card setups, but Nvidia does not for the most part. So you need 2 of the same base cards, makers dont matter.
Could a EVGA gtx 660 FTW be SLI with a EVGA gtx 660?
Yes, that is a good pairing that should work very well. The cards will sync up their clock speeds to match the speed of the slower card so you will lose the FTW's factory overclock. You can always overclock yourself to regain that overclock on both cards in SLI.