Hi Flappie,
if u press only prt screen , normaly, it should be a screenshot in 3840x2400 , but if u use win+prt scr il well be in 1920x1200.
i progress for the issue, i have two screen ( 2x FHD ) but just one with DSR and DCS want launch with 2 screens ( in the option it's 1 screen ) 'cause when i unplug the second, DCS run correctly.