Personally, I loathe surround, it ruins everything else outside of gaming, makes using multiple browser windows a pain, the start menu will not stay where you put it, you can't fullscreen a video on one monitor, ect.
The great thing about DCS is you don't need surround to run multiple monitors. Make sure you left monitor is the main one, then in DCS just type in your resolution in the box and hit enter.
I'm also not a fan of the ultrawide main menu in 1.5 when using 3 monitors. In the monitor config LUA you used to be able to make the GUI stuff appear where you wanted it to, now if I try to contain it within the middle screen it completely distorts the main menu,