It worked on my old 970 GTX, so your 1080 should do just fine with it. All you have to do is right click your desktop, go to display properties, select the display that is your external display, enable HDR/deep color mode on that display (it will only be available to check on displays that support HDR), and then put Vegas into HDR mode in project settings. From there, of course, you need to add 10 bit media, preferably shot in the rec2020 color space, to the project. Only works in Vegas 16+ and only in Windows 10.

Thanks! I will test this later on.

Make sure Vegas has your color space for your media set correctly. If you drop your media on the timeline and notice that it isn't filling the full 1000 nits of HDR when you drop it on the timeline (you'll see it's cropped to 100 nits or less), but it is 10 bit media, you may need to right click on the media, go into its properties, and specify its color space. For instance, when I shoot timelapse, my camera can't shoot Rec2020 color space, but it can shoot AdobeRGB, which is extremely close to it. So, if I go into my media properties and set the stills from my camera to "rec2020" in Vegas' color space options, it then expands the values to fill the full 1000 nits (crops them at 100 nits otherwise). From there, grade away!

Anyway, back on topic... Hardware acceleration!

I don't want to start a new topic, just to point out that I can't use H.265 footages in Vegas 17. In Vegas 16, H.265 works normally, but in Vegas 17 it's very, but very stuck/laggy.
I have to be careful not to set the camera to H.265 :)

@AlesCZ If you didn't already tried, maybe this can help you, https://www.vegascreativesoftware.info/us/forum/vegas-pro-17-bandicam-hevc-files-unsupported--116964/#ca728303