looks like this on the back with the red and white line in?
https://content.hwigroup.net/images/products_larges/180630/5/edifier-r1600t-plus-black.jpg
if so then yeah what i describe will work. you dont need to switch anything in windows, it all goes to the DAC via optical. use the volume knob on the DAC to supply the headphones and the RCA out on the DAC is just a passthrough so just use the volume knob on the speakers to control those.
https://content.hwigroup.net/images/products_larges/180630/5/edifier-r1600t-plus-black.jpg
if so then yeah what i describe will work. you dont need to switch anything in windows, it all goes to the DAC via optical. use the volume knob on the DAC to supply the headphones and the RCA out on the DAC is just a passthrough so just use the volume knob on the speakers to control those.