Windows 10 is the choice. But its still not good. After every windows update you will run into some new stupid complication. If i were you i'd try to split up the cards on two rigs, keeping each rig either Nvidia or AMD. Your downtime with stupid problems would be cut in half. If not more.
You can turn off win10 updates completely. I mean completely, not just delay them. I don't know if there are any significant hash rate differences between win10 & win7 tbh. I'll start GPU mining this week and see if I'll like win10. Gonna compare my hashrate with the other w10 users on the internet. If I don't like it, I'll try win7 secondly. If I see a hashrate drop I'll try ubuntu. If i hate ubuntu somehow, I'll go back to win10.