DT is color managed. The profiles are there to handle that. Your display will normally be the ICC that comes with your monitor or better yet one that you can make from a calibration. Your sensor data is handled by the correct input profile again camera specific or one you make from calibration. Now working profile is usually a wide space to allow room for calculations so rec2920 or prophoto…To monitor gamut you want your histogram to match this…it will then show you as you work if you go out of gamut in this large space. Gamut warnings come from the histogram profile. Your output and export profiles should be set to match your desired out put…these profiles will map your colors from the larger working space to the desired output space. Softproofing is really more about printing…selecting it replaces temporarily your display profile to indicate what your printed output might look like and allow you to adjust it…it would normally be set with a printer/paper ICC profile…
There is a potential hiccup currently in DT…a bounded display profile can produce false gamut indication as the display profile comes first and passes it’s data to the histogram…not the best order…So in DT true gamut comes from setting your working display and just profiles to rec2020. Your image won’t look right on the screen but this setup will give you the most accurate gamut readouts…
This has been previously described and discussed…