I dont have that type of computer. However what you want is for the application feeding DPS to be at 100%. Then use system / computer main volume to control level from DPS to a desired level for your speakers.
Because these headphones require a little more amp volume this profile was done with the DPS volume at 100% and a external DAC with independent volume control.
However the DPS volume does adjust the same location in the signal chain.
Hope this helps and please let us know what you think.
What exactly do you mean by optimal volume?
The output of the DPS in your computer? Or the level of the applications feeding DPS?