R9 290x2 crossfire with R9 290x



Same thing. The 290X2 is third party adaptations of a dual 290X dual GPU setup, the 295X2 is AMDs official design.

It will still work. For AMD, so long as it is the same chip (i.e. Hawaii XT and Hawaii XT) then it will be able to be put into any CFX configuration up to 4 GPUs.