I can confirm that I have been partially successful in making the Asus Z270-P work with 6 Palit 1060 cards - with one big caveat - two of the cards, GPU0 and GPU2, are only hashing at half capacity.

The jury is still out on whether I'm having hardware or software issue - or both.

I think I'm having several issues at once, which kind of make it hard to track down. I changed two of the cards from 1070's to 1060's in the hope that managing just one type of cards would simplify things but they didn't. I'm also having issues with SMOS web interface changes not pushing through to the rig - it remains stuck on the same algo/currency/pool even though I try to change the rig group to something else, and the OC and Watt settings have no effect. But the strange thing is that the rig reboots after changing the settings, just as if it was restarting because of the changes - but everything remains the same when inspecting the console. This seems like a SMOS issue, but I can't be sure.

The two GPU' s running at half speed could be a nicehash related issue, as some googling around have revealed that people have had issues with this when mining to nicehash. Easiest thing to do would be to change to another pool to see if that made a difference, but then SMOS is refusing to push pool setting changes through, leaving me stuvk with nicehash ATM. Bit of a catch 22.

I was thinking I'd try Pimp OS as soon as I have a little spare time just to see how that affects things, but ATM I don't have much spare time...