A single DP1 will struggle with the 21 coach load. The DN Seshadri towards BZA manages it's punctuality well, but the UP Seshadri to CCT struggles with punctuality as it is usually delayed at BZA. The twins help reduce the delay, which would otherwise blow up if a single DP1 is used.
They are cleared for120kmph, but due to some ride quality issues, usually run at lower speeds. I've only ever checked the speed on the SLO-CCT stretch, where it touches about 100 kmph, but I have experienced faster runs on the main line.