it is possible to mine with different video cards. I myself mine with a Sapphire R9 290 and a Sapphire R7 260x
parameters for each card can be set in the cgminer.conf file for example:

"intensity" : "20,20,",
"vectors" : "1,1,",
"worksize" : "256,512,
"kernel" : "scrypt,scrypt,",
"lookup-gap" : "2,2,2",
"thread-concurrency" : "8192,29500"

1st value is for gpu0, 2nd for gpu1 . cgminer I start with a bat file like

setx GPU_MAX-ALLOC-PERCENT 100
setx GPU_USE_SYNC_OBJECTS 1
cgminer --config cgminer.conf

this setup works pretty fine for me