Deep Sleep is there to put monitor into a sleep state where Dell can claim .5W power draw, however you cannot wake the monitor from deep sleep if the PC is still on, you'll either have to power cycle the monitor or restart the machine afaik.
Detailed in here
Apparently Deep Sleep disables the GSYNC module, so if the PC is on and the monitor goes into deep sleep you cannot wake it with mouse or keyboard. I had to disable Deep Sleep in the OSD, many times I need the PC on in the background but am happy for the display to sleep.
As for the other issue, no idea sorry.
Detailed in here
Apparently Deep Sleep disables the GSYNC module, so if the PC is on and the monitor goes into deep sleep you cannot wake it with mouse or keyboard. I had to disable Deep Sleep in the OSD, many times I need the PC on in the background but am happy for the display to sleep.
As for the other issue, no idea sorry.