It's better if you do use the risers to ease on your mobo (less current goes though it = less chance of frying your mobo) , so yes, power the risers.
I know this already. You probably did not get what I am asking. Yes I am using riser cables AND they have the molex connector. My question pertains connecting the molex vs. PCIe power connectors. Do I need to connect molex if I have connected all the GPUs to PCIe PSU coonectors?
As for your second question... if your PSU doesn't have enough PCIe power connectors for all your GPUs, than yes, obviously use it.
I have enough for each gpu. See my question above