What risks from an SMC reset?
Will I lose some settings/configurations?
No.

Do I need to back up some data?
Well, you should always have backup of important data. When it comes to SMC reset it does not touch your storage/hard drive. So no data should be affected.

Is there any risk that the system will not work properly after the reset?
There is a very slight risk. In 99,9999% of all times, if the computer are working perfectly and has no hardware issues the computer till work 100% properly after SMC reset. However there has been cases where the SMC reset fries the logic board, although, those cases had shown other hardware symptoms.

The SMC is responsible for these and other low-level functions:


Responding to presses of the power button
Responding to the display lid opening and closing on portable Macs
Battery management
Thermal management
The SMS (Sudden Motion Sensor)
Ambient light sensing
Keyboard backlighting
Status indicator light (SIL) management
Battery status indicator lights
Selecting an external (instead of internal) video source for some iMac displays