Yes, you can mix cards without a problem as long as the cards are all supported by the drivers you install e.g. on Windows the current Crimson ReLive drivers support all GCN and up cards, so you can mix any of those together on the same rig. On Linux (ethOS and smOS), the current AMDGPU PRO drivers only support GCN 3 and up cards. You will obviously need to set diffrent configurations for the diffrrent cards, so it's simpler to use the same type of cards in a single rig. You can also run AMD and Nvidia cards on the same rig. I currently have RX 480's, HD 7850 and a GTX 1080 on the same rig without a problem.
Thanks Vann, good to hear. So the 'GCN 3 and up' part... are the cards I mentioned above suitable for use on ethOS? GCN 3 isnt something I have read about before..
I was planning on, during initial set up, plugging each GPU into the rig individually to set up with ethOS, then swap out for the next card and so on until all cards have individually been configured, then once they are all done id then plug them all into the rig together?
Thanks