[Dan Davis]"HD delivery at the moment. But if I was asked to deliver HDR can I monitor to an extent using the monitor I have?"
My opinion is no. You have to actually calibrate the monitor for SMPTE 2084 and/or 2020 for HDR/extended color gamut. It won't work with a display designed for Rec709.
I personally wouldn't worry about it until such time that HDR becomes a big delivery requirement. In theory, you will be able to hook up an HDR display then change the output gamut/gamma of Resolve, then do a trim pass to compensate. The chapter on HDR & Dolby Vision in the 12.5 manual (pp. 177-190) go into a lot of detail on the issues involved. I'm not convinced a $995 Costco "HDR" display is going to work for color grading.