You can mine with different cards, no problem.
It has no metter if you use pci-e 3.0 or 2.0., for mining you don't need even pci-e 16x slot, it's good with 1x too, just need powered riser for that.
Can I ask, all new high end video cards for GPU mining can use 1x pci-e slots? That means it's the short connection? And all GPUs can use powered risers that fit pci-e 1x?
So I can use almost any motherboard that has a bunch of pci-e slots, because the smallest one is 1x anyway?