Most of the time (DL)DSR and DLSS are used simultaneously to compensate for the lack of a DLAA option, which not many games support natively.
Often times this is done since DLAA is a much better AA solution comapred to TAA for example. Since DCS already supports DLAA out of the box, there's not too much use for that method.
For example, 1440p + 2.25 (DL)DSR + DLSS Quality = 1440p, which is identical to 1440p + DLAA resolution and AA wise. But the latter one most likely provides better performance.
