Thank you for the help. One question: is there way to set constant fan speed (i.e. 50%) in OverdriveNTool? Cause those spining and stoping down fans, makes me crazy ...
Maybe I'm a little late here and you have already figured it out.
I've not tried this but here is a suggestion, set both Min and Max fan rpm to the same value (e.g. your 50%) then set the Target Temp to well below ambient temperature, say 0 degrees. This should force the fans to come on and stay at the 50% rpm.
My mining rig room is about 18C and cards stay <60C. These are a mix of Nitro+ 580, Gaming X 580 and Strix 570s.