the group boilers do not need to be drained each morning, they hold 1.2 ltrs and the +4U flushes the system each time you turn on the machine. BUT you should not turn off the +4U as the energy saving system completly controls the machine and "it knows" when the machine is in rest and turns down the tempratures to save energy.
as for the steam temprature, can set it from 0.9 bar to 1.4 bar, the real benifit is that depending how powerfull you want the steam pressure is easily adjustable in the display. I would suggest you start at 1bar and see which setting suits you best.
the two tempratures group and water resiviors allow you to fine tune the machine for extraction +/- 0.5 degree, and it allows for envorimental factors ambient room temprature for example.
hope this explains, if you need to know any more ASK away!!